Usability Study

• Experiment Design
• Usability Testing
• Results and Feedback
• Changes Made

Experimental Design

Variables:
We will change the way the slide bar on the tips page snaps and keep everything else the same. The three cases, or independent variables, will be:

• Snap to single percent (1, 2, 3, ...30)
• Snap to tip amounts that cause the total to become a "nice number" (an amount ending in .00, .25, .50, or .75)
• (On "Split All Evenly") Snap to amounts that make individual totals be nice numbers.

The dependent variables would be:

• When I first saw the screen, I quickly understood how to select a tip.
  
• The tip slider is easy to use.
• The tip slider allowed me to select my desired tip.

If our hypothesis is correct, then we would have high ratings for question 3 but not question 1. We are planning on having participation from at least 5 people who haven't used the system yet. The people who have used the system have already provided opinions on the interface and may have bias for or against it already. We will tell the users the background for the system and then show the tips interface to people to play around with. Afterward, we will pass them a short survey to gather data.

Usability Testing

We decided that the best way to test the tips page would be a survey since there is really no objective way of measuring the satisfaction of use.

The test cases can be found here.

Testing results and Feedback

We tested the the tips page along with the whole prototype on 7 people. Below are the compiled survey results and the numbers are the number of people that selected that choice:

We attempted to quantify this data by assigning a scorring system, where the comments were matched as follows:

• 1 - Strongly Disagree
• 2 - Disagree
• 3 - Neutral
• 4 - Agree
• 5 - Strongly Agree

The plot showing the total (normalized) score of each situation is below:

Although the "Snap to $0.25 paid" choice scored the highest, the score is not significantly higher than "Snap to 1%", our control case. Also, the number of people who went through our entire test was very small, and therefore the data overall was not significant enough to give any conclusions. Because of this, we did not change our prototype in response to this experiment.

Overall prototype impressions

Because our quantitative data was inconclusive, we used the usability testing phase as a chance to get more feedback of our design overall. This led us to many comments that were much more helpful, and led to some interesting prototype changes.

Changes Made

There seems to be no conclusive result from our tips page experiment. In general, users seems to be fine with the way it is. The experiment over the whole prototype raised a few questions about what we should change about our prototype:

• Some users could find the paycode, but didn't understand what to do after the "return" was pressed on the keyboard. To make the next step (clicking 'Next') more evident, our prototype now displays a green text "Valid Paycode. Click next to continue" when the correct paycode is entered, giving the user assurance that they are doing things right.


• Many users said the tip slider not sliding all the way was a bit obnoxious; they felt like they should drag all the way to the edge. However, allowing this would cover up some of the text at the end, so we rearranged the tip slider layout so that this could be done aesthetically, without eliminating important information


• One of the users mentioned that upon first entering the screen, he was temporarily unclear what "split unclaimed items" do. Since it is easy to implement and we feel like it would help many users, we decided to add an instruction in the beginning.



(Left: Modified, Right: Original.)
• Some users found the "edit customers list" option a bit clunky, and were sad that it was required for people to edit this list when they had more or fewer than 6 guests to work with. In response, we created an initial "choose number of customers" screen for the "Split by items" page. Because you always know how many people are eating up front, it is always the case that you can provide this information initially and easily.