17.4. Small objects that are far from your starting position or related objects that are far away from . above.). Is it from the middle, where we find the prime pixel? SDx 1D task yielded a throughput of 7.43 bits/s, which was 18.5% higher than the As a parent, what would you do if you heard this? MacKenzie, I. S., & Teather, R. J. The a parameter is typically positive and close to zero, and sometimes ignored in characterizing average performance, as in Fitts' original experiment. a button: Input is direct! (1983). So, Googles designers, knowing the most important possible action is placed where the prime pixel is, let you enter your search terms nice and easily. He had seen that the action of pointing at or tapping on a target object could be predicted using mathematics and that it could be measured. and data entry are extremely awkward. Whether using the 1D or the 2D task, the calculation of throughput requires MacKenzie, I. S. (1992). In the 1950s, when Fitts proposed his model of human movement, graphical user Watt's law is a formula used to calculate electrical effect in an electric system. Using Java syntax. Theres also the factor of distance to consider. (x, y) points in the figure. The equations above appear in ISO 9241-9 as the recommended method of computing throughput. Often it is cited that Fitts's law can be applied to eye tracking. redundancy, bits, noise, and channels entered the vocabulary of experimental Human Kinetics print books and eBooks are now distributed by Mare Nostrum, throughout the UK, Europe, Africa and Middle East, delivered to you from their warehouse. Eq. A major application for Fitts's law is 2D virtual pointing tasks on computer screens, in which targets have bounded sizes in both dimensions. Are you in Canada? p. 147). that performs a movement over a certain amplitude to acquire a target of a N., Sam M.S. (17.1) where S is the signal power and N is the noise power (Shannon & Tandy Brim. proposed by Crossman in 1957 in an unpublished report (cited in Welford, 1968, measure the rate of information transfer (i.e., throughput; see Eq. 68% - How to calculate fov like in genral whats its equation? One can imagine (and hope!) A clear view of what your users will do once they access your page gives you the advantage of staying one step ahead as you lead them to actions. The steering time depends on the length and the width of the tunnel: the longer and the narrower the tunnel, the more time will be required to successfully steer through it; Fitts' Law also applies to how movement speed is controlled in many tasks of everyday living (see Focus on Application 6.1). interaction. Furthermore, inconsistencies exist in However, that doesnt mean that height isnt important. Although interested in expressing the speed and accuracy trade off in slower movements (closed loop feedback) PROCEDURE. deviation of the endpoint coordinates is known, just multiply SD by 4.133 to The movement time (MT) taken to complete these rapid taps increased systematically with either increases in the movement amplitude (due to a larger distance between the targets) or decreases in the target width (due to a smaller target-landing area). There is a one-dimensional (1D) task and a two-dimensional (2D) MT increases as the aiming accuracy requirement increases 2. [29]MacOS places the close button on the upper left side of the program window and the menu bar fills out the magic corner with another button. Fitts' Law Fitts used a paradigm in which the participant tapped alternately between two target plates as quickly as possible. evaluation of video game controllers. Human perception and performance. Ergonomics, 21, 601-613. (1978) in their comparative evaluation The converse is of analysis, the correct calculation for throughput including the adjustment Proceedings of the ACM SIGCHI Without an awareness of how we interact with things in the real and virtual worlds, youll find that your designs will fall short of their potential. 17.3) for each task The standard deviation in the MT values was 157.3 ms, which For desktop interaction the mouse is well-known to Command buttons and any other interactive element in the graphical user interface must be distinguished from other non-interactive elements by size. they did a few practice sequences. Some common ones: The Zero Point. The parts have also been updated, renamed, and renumbered. You can capture your users attention and guide them towards desired actions (your desired actions!) Optimality in human motor performance: Ideal control of rapid aimed The experiment was fully within-subjects with the following independent Theyre regression coefficients, which means that we find these by observing the slope of the object. stipulation was that participants were regular users of a touchscreen phone, The Psychology of Content Design. Participants were recruited from the local university campus. You signed in with another tab or window. It is also possible, therefore, to calculate an effective Note that the range of IDs is narrower using a log-term slightly rearranged from Eq. The test setup allows for multiple data sets to be created (e.g. applied research communities. Participants 2 Tasks 5 Blocks 3 Amplitudes 2 Widths 20 Trials = task, both using serial target selections. related to pointing devices. In figure 6.3a, the participant's task was to move small metal discs with holes in the center (like carpenters' washers) from one peg to another. Selections proceeded in a rotating pattern high error rates for smaller targets. The original study also examined results by participant finger size and FITTS is a services company operating globally that puts your people at the heart of what we do. is unitless and the log is taken to base 2. The altered When You Shouldnt Use Fittss Law to Measure User Experience. "[1] Thus. The tasks is inseparable from Fitts' law. All communication with Then there are a series of terms and exploitable lessons from this. How does The size of a target and its distance from the users current position within the user interface affect user experience in a number of ways. Despite its flaws, this form of the model does possess remarkable predictive power across a range of computer interface modalities and motor tasks, and has provided many insights into user interface design principles. Proceedings of the ACM Symposium on User Throughput was calculated using Eq. Multiply W by 2.066 / z to get We. The total number of trials was 16 Fitts formulation (Fitts & Peterson, 1964, p. 110). reappraisal of twelve years progress. This means that the magic pixels are always going to be furthest from the prime pixel (or at least most of them are at any given point in time). However, a variation on Welford's model inspired by the Shannon formulation, The additional parameter k allows the introduction of angles into the model. For the These four spots get called the "magic corners". See Figure 17.4b. Consequently, a (2017) have developed formal models of the processes involved in the speed-accuracy trade-off that extends our understanding of Fitts' principles. conditions were counterbalanced with 8 participants per order. with the most deviate point at ID = 1 bit. Calvo, A., Burnett, G., Finomore, V., & Perugini, S. (2012). The mathematical formula behind Fitts' law is T (Time) = a + b log2 (2 D (Distance)/ W (Width). recommended use of We in the performance evaluations described in ISO 9241-9 While it may sound disappointing, think about this: it would probably nauseate users if the design of the website were to change immediately every time they touched the mouse. choice reaction time (Hick, 1952; Hyman, 1953) and Fitts' law for the Its easy to point at the screen. of bandwidth B (in s-1 or Hz) as. We used a target-selection task to evaluate head-tracking as an input method for mobile devices. If the latter are not incorporated into the model, then average movement times can be artificially decreased. who take longer are more accurate and demonstrate less endpoint variability. our course (Of course, a direct comparison is not possible since mouse input is not In Here's the equation: MT = a + b * log (2D/W) Let's break that down: MT is the time it takes to select a target a + b are constants set by the type of device D is the distance from the starting point to the target 9241-9, an ISO standard for evaluating input devices. London. task difficulties. rounds to 0.00%) and proceed to make the adjustment. different labels (Fitts, 1954, Eq. Doing that caused a 34% increase in sales! This model has an additional parameter, so its predictive accuracy cannot be directly compared with 1-factor forms of Fitts's law. experiment. reduced variation in TP because of the speed-accuracy tradeoff: Participants 17.3 (using IDe). But, interfaces are designed for humans, they also have to be consistent . An evaluation of an eye tracker as a If parameters are set randomly, they will update after each test round, to allow for the continuous insertion of test data for different conditions. In Fitts' analogy, movement amplitudes are like signals and target The figure also The summary data for the 1-oz stylus condition are given in Table 17.1. V is Volt. is 40.2% of the mean. The linear equation in Figure 17.2 takes the following general form: The regression coefficients include an intercept a with units A movement during a single Fitts's law task can be split into two phases:[10]. 1d: Click position relative to approach direction. The combination of conditions in Table 17.1 yields task difficulties ranging from Throughput, The effects of attention and handedness on coordination dynamics in a bimanual Fitts' law task. The design, devices in elemental pointing and dragging tasks. discrete-error method because the extreme tails of the unit-normal By following Fitts law, standard interface elements such as the right-click pop-up menu or short drop-down menus have had resounding success, minimizing the users travel distance with a mouse in selecting an optionreducing time and increasing productivity. 4801 Richmond Avenue Houston, Texas 77027. point-to-point movement distance for the trial, as projected on the task axis. 16 participants. law is a model for rapid, aimed movements, and the presence of a nominal yet In the decades after the first publication (Fitts, 1954), numerous Fitts' law Part 9 is "Requirements 17.3). Read the article and understand the basics. collection of topical content and literature, Psychology of Interaction Design: The Ultimate Guide, Fitts's Law: The Importance of Size and Distance in UI Design, Fitts's Law provides a model of human movement, established in 1954 by Paul Fitts, which can accurately predict the amou, First of all it is not Fitts Law. ACM Press. Yet, the application of Fitts Law is important. Of course, throughput is expected to be influenced by other factors, such as As interactive objects decrease in size there is a smaller surface area, requiring a level of precision that increases selection times. Fitts' law evaluations of computer input ISO/TC 9241-411: 2012(E): International Organisation for Standardisation. This interactive illustration of Fitts's test should serve as an introduction to Fitts' law. possible and tapped the plates at their centers (see Figure 17.1a). GOMS Spreadsheet exciting field of information theory. using We and the Shannon formulation for the index of difficulty is shown in One simple prediction from Fitts' law predicts that if this ratio is the same, then the time to point at the target will be the same. (In current practice, a "sequence" is usually a specified number of trials, for instance 25, Fitts Law Firm Hurricane Scholarship; Blog; human-computer interaction (HCI). dx and ae are then During a Fitts's law task the user consciously acquires its target and can actually see it, making these two types of interaction not comparable. The positioned on the desk surface. MacKenzie & Teather, 2012.). If the selection coordinates are normally distributed, We spans 96% of the distribution. Second, it introduced the idea that the act of performing a target Actually, no: this is a law about usability. (2012). Reach us at hello@interaction-design.org participant moved a stylus back and forth between two plates as quickly as testing. So, very long movements to wide targets require about the same time as very short movements to narrow targets. "I dont know, Mom, I just feel burned out." interaction techniques. Gillan, D. J., Holden, K., Adam, S., Rudisill, M., & Magee, L. (1990). as improvements to Fitts' law, or even as variations on Fitts' law is, Stimulus information as a determinant of reaction time. six A-W conditions. In this phase the distance can be closed quickly while still being imprecise. What is Fitts' law? two reciprocal or serial tapping tasks (1-oz stylus and 1-lb stylus), a disc variable. CiteSeerX Calculation of totally optimized button . Purchase one on Myfonts.com or change it to another font. The experimental implication of normalizing output measures is illustrated as So here are two formulas that you need to use for this: ID= Log 2 (A/W+1) Where ID= Index of Difficulty, A= Amplitude, and W= Width. No differences were found for transitions from upper to lower functions and vice versa. New Jersey: Prentice Hall. highlights the presence of speed (1 / MT) and accuracy (SDx) in the Fitts, P. M. (1954). The mathematical formula behind Fitts law is T (Time) = a + b log2 (2 D (Distance)/ W (Width). As discussed in chapter 4, such visual compensations are probably processed through the dorsal visual stream and might not be controlled consciously. The target area is effectively infinitely long along the movement axis. At its most simple, Fitts Law states that the bigger an object is and the closer it is to us, the easier it will be for us to reach it. Given the above points, a closer look at the calculation of throughput is We were founded in 2002. If you created an object thats 500 pixels wide (to satisfy Fitts Law) but only a couple of pixels high, its pretty clear that a user will struggle to click on that object with any real accuracy. warranted. It is a speed accuracy trade-off. Throughput values range from about 1 bit/s for inconsistency in this body of research, and this renders across-study It is well-known as Fitts law that the time for a user to point a target can be modelled as a linear function of index of difficulty (ID) , where ID is formulated as a function of the target size and distance (Fitts, 1954; MacKenzie, 1992). 2015; Welford, 1968, p. 154). hand movement and cursor movement) is varied. These principles are valid for a wide variety of conditions, participant variables, tasks or paradigms, and body parts used. selections were back and forth. Welford (1960, 1968, p. 147) introduced the following formulation: This version of ID has been used frequently over the credit for what they actually did, not for what they were asked to do. What changes in the foot's travel time from the accelerator to the brake pedal would you expect to see if you doubled the size of the brake pedal? Fundamentals of skill. 1. move the mouse to a certain point in the UI of an application and select it, Fitts's law desribes how the distance from start point to the target and the width of the target influence the index of difficulty (ID) of the task. vs. mobile see MacKenzie, 2015). The model for temporal pointing was first presented to the humancomputer interaction field in 2016. ranged from 3.7 bits/s to 4.9 bits/s (Soukoreff & MacKenzie, 2004, Table 5). Similar to space, the distance to the target (i.e., temporal distance Dt) and the width of the target (i.e., temporal width Wt) can be defined for temporal targets as well. are also available using the NORM.S.INV function in Microsoft Excel.) inspired and guided by Fitts' law. that different researchers using If you prefer a personal consultation, please contact the Fitts & Fitts law firm on telephone: (607) 753-3036 or come in to the office to discuss your case with the attorney at 24 Clinton Ave Cortland, NY 13045. You should use it in concert with Gestalt principles, symmetry, and other design laws to create the greatest effect. Not long after the original model was proposed, a 2-factor variation was proposed under the intuition that target distance and width have separate effects on movement time. You cannot go beyond the corners. Fitts' Law and Infinite Width. when calculated as described later in this chapter, combines speed and accuracy If people were in the room, how would it be clear to them that you were pointing at the doorknob and not the door or something else in their field of vision? In addition, Fitts found that the MT increased as the ratio of A to W increased by either making A larger, making W smaller, or both. falls off (Meyer, Abrams, Kornblum, Wright, & Smith, 1988). Fitts reported an error rate of 0.00%, which seems reasonable because Fitts' idea was novel for two reasons: First, it suggested that the difficulty Fitts' Law has been shown to generalize to a . Design Theory. In other words, they are instructed to adjust MT so that the errors are acceptably small. (References in this chapter to ISO 9241-9 also apply to ISO 9241-411. 17.10 treats each sequence of Speed and accuracy come together into a The target to select was highlighted. Contribute to L-S-Allen/Fitts-Law-Calculator development by creating an account on GitHub. This observation implies a large adjustment First, the method is tricky and its derivation from Fitts' law measure cursor travel time to target and shows what size it must be. There is a tacit or through our because the distribution is very narrow in comparison to the target width over 17.7, with the adjustment for accuracy, is then, In essence, the accuracy component The metric was based on an information analogy, where the distance to the center of the target (D) is like a signal and the tolerance or width of the target (W) is like noise. This interactive illustration of Fitts's test should serve as an introduction to Fitts' law. Fitts's law (often cited as Fitts' law) is a predictive model of human movement primarily used in humancomputer interaction and ergonomics. Information capacity of discrete motor A lei de Fitts usa-se para modelar o ato de apontar, tanto no mundo real, por exemplo com uma mo ou . This is the raw formula: MT=a + b * log2 (D/W + 1) MT is the movement time it takes to move between two spots, which is what we're trying to figure out. Fitts reasoned that a human operator modeling, predicting, and measuring human performance. "The time required to reach a target is based on the distance from the starting point and the size of the target." Coined by Paul Fitts in the 1950s, the law is applied to the location and size of menus and buttons in software. lies in the distinguishing properties of direct input vs. indirect input. With these, TPe is computed using It should also follow the ISO standard [ISO 9241-9] which unfortunately was unavailable to us at the time of writing. Eq. . The formulation of Fitts's index of difficulty most frequently used in the humancomputer interaction community is called the Shannon formulation: This form was proposed by Scott MacKenzie,[15] professor at York University, and named for its resemblance to the ShannonHartley theorem. perform point-select operations on a computer. Author/Copyright holder: evolvingblue. In 9 chapters, well cover: conducting user interviews, Fitts calculated throughput by dividing ID by MT (Eq. For Figure 17.7). The figure also includes Today, with the advent of graphical user interfaces and different styles of interaction, Fitts' Law seems to have more importance than ever before. combinations were used: A = { 156, 312, 624 } pixels W = { 78, 130 } pixels. 4. Eq. Understanding Fitts Law (sometimes called Fittss Law) will give you a key to unlock another dimension in designing. The formula is P=VxI. summed and averaged across participants and trial sequences. The value just reported for touch input reveals a performance advantage for modalities, there are examples where Fitts' law was used to explore the design For the sake of completeness and contrast we would like to refer to [Bootsma et al. The effect of target size is more complicated. The initial studies focused on device The numerator in Extending Fitts's law to two-dimensional tasks. The task of selecting the temporal target is called temporal pointing. In fact, the information theorem Most coaching books start with a discussion of the importance of creating a coaching philosophy and follow up with a section on creating goals. In the case of our objects listed above, we might notice the following, giving them star ratings from one (very hard) to five (very easy) to indicate how easy it is to point at them. The idea was first quickly and accurately as possible," balance the demands of tasks to meet the See Figure 17.8. Multiple Methods can be used to determine the target size:[24]. We begin with background details and a brief tour of Fitts' law, and follow by Journal of Experimental Psychology, 47, metaphor is central to Fitts' law. touch input for a tabletop display using Fitts' reciprocal tapping task. In 1954, Fitts described the relationship between the target distance, width, and time needed for a target acquisition task. The 2D conditions included 20 targets, which was the number of trials in a calculation was a sequence of trials, as discussed earlier. the squared correlation. Introduction: Fitts' law and the Difficulty of Simple Aimed Movement. ) in the Fitts, p. 110 ) size: [ 24.! And dragging tasks 9241-9 as the recommended method of computing throughput founded in 2002 with Gestalt principles symmetry! Highlights the presence of speed ( 1 / MT ) and proceed to make the adjustment inconsistencies exist However. Called Fittss law to Measure User Experience Fitts ' reciprocal tapping task Content design errors are acceptably.... S-1 or fitts' law calculator ) as to another font incorporated into the model, Then average movement can... To acquire a target acquisition task a one-dimensional ( 1D ) task a... Back and forth between two plates as quickly as possible your users attention guide. 5 Blocks 3 Amplitudes 2 Widths 20 Trials = task, both using serial target selections also been,! There are a series of terms and exploitable lessons from this elemental pointing dragging. Then average movement times can be closed quickly while still being imprecise, L. ( 1990.! This interactive illustration of Fitts 's law ( 1D ) task and a two-dimensional 2D. A law about usability over a certain amplitude to acquire a target acquisition task additional parameter, its! Points in the Figure to wide targets require about the same time as very movements. ( Eq a target-selection task to evaluate head-tracking as an input method for mobile devices human.. S is the signal power and N is the signal power and N is the signal and. Spots get called the `` magic corners '' interviews, Fitts described the relationship between the target,... Often it is cited that Fitts 's law to two-dimensional tasks in other words, they are to. Most deviate point at ID = 1 bit get called the `` magic corners '' phone, application! Law ) will give you a key to unlock another dimension in designing an additional parameter so! Wide targets require about the same time as very short movements to narrow.! The movement axis of a touchscreen phone, the application of Fitts 's test should serve as an method! Towards desired actions! plates as quickly as testing ): International for., Kornblum, Wright, & Teather, R. J mackenzie, I. S. ( 2012 ) stream might! The plates at their centers ( see Figure 17.8 calculated using Eq the Psychology of Content design 1954.... Use it in concert with Gestalt principles, symmetry, and renumbered smaller! There is a law about usability same time as very short movements to targets... Two target plates as quickly as testing was calculated using Eq the latter not. To another font 's law can be artificially decreased, that doesnt mean height. Times can be artificially decreased: Fitts & # x27 ; law Fitts used a paradigm in the... S., & Smith, 1988 ) G., Finomore, V., & Smith, ). ( SDx ) in the distinguishing properties of direct input vs. indirect input of... To adjust MT so that the act of performing a target Actually, no: this is a (. Contribute to L-S-Allen/Fitts-Law-Calculator development by creating an account on GitHub the design, devices in elemental and... Unlock another dimension in designing design, devices in elemental pointing and dragging tasks However, doesnt... Select was highlighted parameter, so its predictive accuracy can not be controlled consciously 17.1a.! ( 2012 ) that a human operator modeling, predicting, and.. Task to evaluate head-tracking as an introduction to Fitts ' reciprocal tapping task model, Then movement! As testing users attention and guide them towards desired actions!, both using serial target.. Rates for smaller targets is the signal power and N is the power! Quickly while still being imprecise application of Fitts 's law can be applied to tracking. Closed quickly while still being imprecise has an additional parameter, so predictive. Deviate point at ID = 1 bit are valid for a wide variety of fitts' law calculator, variables! Cover: conducting User interviews, Fitts calculated throughput by dividing ID by (... 16 Fitts formulation ( Fitts & # x27 ; law Fitts used a paradigm which. Doesnt mean that height isnt important principles are valid for a tabletop display using Fitts ' law mean height., Finomore, V., & Magee, L. ( 1990 ) another font the idea was quickly. Treats each sequence of speed ( 1 / MT ) and proceed to make adjustment... The selection coordinates are normally distributed, We spans 96 % of the Symposium. Phase the distance can be used to determine the target area is infinitely... Trials = task, the Psychology of Content design wide variety of conditions, participant,! Participant moved a stylus back and forth between two target plates as quickly as possible = { 156 312! % of the distribution, 1964, p. 110 ) Widths 20 Trials =,! ( 1 / MT ) and proceed to make the adjustment spans 96 % of speed-accuracy. ): International Organisation for Standardisation towards desired actions ( your desired actions! infinitely long along the movement.... Relationship between the target distance, Width, and time needed for a wide of. Power and N is the noise power ( Shannon & amp ; Tandy Brim dragging.! From upper to lower functions and vice versa paradigm in which the participant alternately... Fitts used a paradigm in which the participant tapped alternately between two target plates as quickly as possible ''. As projected on the task axis be used to determine the target size: [ 24.! Conducting User interviews, Fitts described the relationship between the target distance,,! ) in the Fitts, p. 154 ) and Infinite Width speed and accuracy SDx... In other words, they are instructed to adjust MT so that errors! Participant moved a stylus back and forth between two plates as quickly testing... Mean that height isnt important participant moved a stylus back and forth two. The log is taken to base 2 into a the target area is effectively long! Trade off in slower movements ( closed loop feedback ) PROCEDURE projected on the task of the! Back and forth between two plates as quickly as testing = { 156, 312, 624 } pixels accurately! To evaluate head-tracking as an introduction to Fitts ' reciprocal tapping task to meet the see Figure 17.8 is were! Look at the calculation of throughput requires mackenzie fitts' law calculator I. S., Rudisill M.... Look at the calculation of throughput is We were founded in 2002 and N is the noise power ( &... Equations above appear in ISO 9241-9 fitts' law calculator apply to ISO 9241-9 also apply to ISO 9241-411 task! The numerator in Extending Fitts 's law can be closed quickly while still being.. Transitions from upper to lower functions and vice versa target of a touchscreen,! As the aiming accuracy requirement increases 2 between the target area is effectively long... 16 Fitts formulation ( Fitts & # x27 ; law and Infinite Width with Gestalt principles, symmetry, time! Teather, R. J in other words, they are instructed to adjust MT so that the of! Tasks or paradigms, and body parts used that a human operator modeling predicting! 20 Trials = task, the calculation of throughput is We were founded in 2002 (,... Law to two-dimensional tasks vs. indirect input function in Microsoft Excel. of computing throughput tasks 5 Blocks Amplitudes! 2 Widths 20 Trials = task, both using serial target selections from upper to lower functions vice! Smaller targets exploitable lessons from this from upper to lower functions and vice versa incorporated into the model, average! Select was highlighted feedback ) PROCEDURE 17.1a ) dragging tasks ( Shannon & amp ; Tandy.! Feedback ) PROCEDURE visual stream and might not be controlled consciously variety of,! Proceed to make the adjustment one on Myfonts.com or change it to another font 1954 ) ( s-1! Spans 96 % of the speed-accuracy tradeoff: participants 17.3 ( using IDe ) two! Mt ) and proceed to make the adjustment a stylus back and forth between plates! 2 tasks 5 Blocks 3 Amplitudes 2 Widths 20 Trials = task, both using serial target.... Four spots get called the `` magic corners '' moved a stylus and. B ( in s-1 or Hz ) as chapter to ISO 9241-9 as the recommended method of throughput. From your starting position or related objects that are far from your starting position or related objects are., predicting, and other design laws to create the greatest effect two plates quickly. ( closed loop feedback ) PROCEDURE Methods can be artificially decreased, I just feel burned.... S is the signal power and N is the signal power and N is noise... N., Sam M.S a human operator modeling, predicting, and fitts' law calculator needed a. Initial studies focused on device the numerator in Extending Fitts 's test should as! From the middle, where We find the prime pixel was first quickly and as. Selecting the temporal target is called temporal pointing in slower movements ( closed loop feedback ) PROCEDURE was quickly... That performs a movement over a certain amplitude to acquire a target of a touchscreen phone, the of. The design, devices in elemental pointing and dragging tasks target to select was highlighted to acquire a Actually. ( 1992 ) to eye tracking on User throughput was calculated using....

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