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This report provides an analysis of information theory and decision making and uses this to redesign an ATM machine for optimum speed for cash withdrawal. Methods of analysis include calculating the index of difficulty, usage of design tool, usage of excel to calculate the linear equation, calculation of channel capacity and finally redesigning the ATM machine. All calculations can be found in appendices. Results of data analysed showed that the average reaction time increases with increase in number of alternatives, button width and distance apart.

This report finds the current design of ATM machines are not very efficient to withdraw fast cash. After conducting several tests with our knowledge in information processing it is recommended that the redesigned version is used because it is the most time efficient solution.

The primary purpose of an ATM is to quickly withdraw cash from the bank. To speed this process of cash withdrawal an ATM machine can be redesigned for optimal speed of cash withdrawal.

Some of the design parameters to take into consideration include form of layout, type of layout and type of entry and size of layout. Several experiments were conducted in order to find out which of these parameters had the greatest effect when optimizing the overall ATM user experience. After all the calculations and results were obtained, a redesign of the ATM was executed and proved to be more efficient.

- Measure the distance between buttons and their respective width to obtain the values to calculate the Index of Difficulty.
- Use Design Tools to run multiple trials with different characteristics varying shape, color, target and distance between objects.
- Record the different reaction times in each trial and graph them according to the amount of information, hence finding the linear equation.
- Using the reaction time equation found in the previous step, calculate the channel capacity and various event alternatives.
- Redesign the ATM panel layout to increase the user’s reaction time and obtain optimal speed of cash withdrawal.

To accomplish the objectives described, several steps were followed.

- The Index of Difficulty (ID) was calculated by obtaining the average distance from the home button (5) to every other number, and the width of one button. Those values were then plugged into the formula for ID.
- After calculating that the smallest ID value, it was decided that the square layout was preferred. Then, Design Tools was used to run different experiments with varying characteristics. The first was choosing two combinations of square measurements and setting different distances between them.
- In both cases the smaller square size and smaller distance resulted in a lower reaction time. Another test that was completed was the simple reaction test with a specific colour. The colour chosen was red and the reaction time for 20 trials was recorded. The last experiment was the Choice Reaction time in which three test of 20 trials were completed.
- The first test consisted on tapping one of two numbers that would appear on the screen, the same for the second test but now tapping one of four different numbers and for the third test tapping one of eight numbers each time it appeared.
- After completing all the trials and recording the correct information, a chart was plotted with the values of the reaction times for each experiment with its related amount of information.
- This graph is plotted. With the equation given by the graph some events were calculated such as the channel capacity, the response time for 10 equally likely alternatives and for a 4 digit number, etc. Finally, with all the information collected we were able to redesign an optimal ATM panel layout that would increase the speed of cash withdrawal.

The results obtained in the evaluations are displayed in the tables below. Table 1 shows the index of difficulty obtained for the square and in-line layout. It was shown that the square layout had a lower index of difficulty with a value of 1.459 against 2.907 obtained for the inline layout. The main reasons for this result rely in the difference of width in the keys and the average distance between the keys. For the square layout the width of the keys were 2 cm, on the other hand the width for the in-line layout was 1cm. The average distance for the square layout was 2.75cm and for the in-line layout 3.75cm.

Using the Design Tools software, the characteristics that affect the efficiency of the processed discussed were observed and analysed. Figure 1 show the results for the Fitts’ Tapping Task module in which the variations used was the size of the square and the distance between them. For the first combination the size of the square was 1.5×1.5 and the distance between the two squares was 3. For the second combination the size was 2×2 and 4 of distance between the squares. When comparing the tables for both combinations it can be observed that the average time for the trials in combination 1 is lower than those in combination 2, as well as the number of errors.

Figure 2 shows the same test performed in the software. The dimensions chosen were those of the first combination since it was shown to be the most efficient of the two events tried. The time spent performing the 100 trials was 17.28 seconds, since no errors were recorded, the formula given for the average time resulted in 0.1728 seconds.

Another test using the Design Tool software was the Simple Reaction Time Module. In this event the colour red was chosen to tap it every time it popped. In Figure 3 the results for this test are displayed, the average time obtained being 0.3691 with a standard deviation of 0.1706. This number was later used as the intercept of the Hick-Hyman Plot.

For the last event the module used was Choice Reaction Time in which the results are the data points used in the Hick-Hyman Plot. The three test for this module differ on the amount of choices you had to tap. The results for the three tests are shown in Figure 4, 5, and 6 respectively.

The first test, which had only two options, had the lowest average time 0.3836. On the other hand, the highest average time was for the third test which had more options resulting in 0.6039.

The channel capacity was calculated as 1 over the slope resulting in a value of 11.806. The response time for 10 equally likely alternatives was calculated by plugging H=10 into the equation of the line, resulting in 1.1907. Furthermore, the result time for a 4 digit number was obtained by multiplying the previous result by 4, getting 4.7628.

Lastly, the response time for 6 key strokes resulted in 5.6196. All these values can be observed in Table 2.

After completing our calculations and trying different experiments, we realized some characteristics could be redesigned in order to increase the efficiency and overall experience using the ATM. Initially, when the Index of Difficulty was calculated for the square and in-line layouts, it was clear that the preferred layout was square, since it had the smallest ID value. From that information, the square layout was the one chosen for all the other calculations. When the Fitts’ Tapping Task was completed, it was observed that there was a relation between the width of the buttons and the distance between them. Although the second combination had a larger width, the first combination had a smaller distance between the buttons. Therefore it was concluded that instead of choosing one of the two combinations, it was better to mix wider buttons with closer distance.

With wider buttons it would decrease the number of errors, and by decreasing the distance it would increase the speed the user takes from tapping one button to the other. To proof the effectiveness of the redesign proposed the index of difficulty was obtained using a bigger width and a smaller distance. With a width of 2 cm and an average distance of 2.5cm the ID results in 1.322 decreasing by some units. Similarly, the values for the reaction time and number of errors, from the Simple Reaction Time and the Choice Reaction Time experiments were obtained with Design Tools

It was observed that as the number of alternatives increased the average reaction time also increased, this is mainly due to the fact that the user has to decide between all the alternatives before tapping their answer, so as the number of alternatives gets larger the time taken to decide will also be greater. This observation is represented in the plotted graph.

It was concluded that for the redesign the buttons should be larger in width and should be positioned closer to one another.

In conclusion, the speed in which the user hits the buttons is increased with wider button and shorter distance. This relation was explained with the experiments made throughout the case study. Reaction time 2 (T2) proved to be the most efficient design for the ATM machine because it took the shortest amount of time to operate on. This is true because the distance between the buttons were made shorter and the buttons were also made wider which decreased the amount of time it took to mock the 6 key strokes. Therefore it is recommended that to use the redesign provided in trial 2 because it is the most time efficient method. Reaction time 3 (T3) is longer because the buttons in a typical ATM machine is wider apart from each other and smaller therefore this increases the reaction time. Reaction time 1 (T1) is similar to reaction time 3 because the conditions of the ATM machine are similar to the conditions under which the tests in T1 were conducted.

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