Development Process for Scale Interface


Low-fidelity Prototype Screens











High-fidelity Transition


The low-fidelity prototype was the skeleton for deriving at the high-fidelity prototype. On some screens, the high-fidelity model differs mainly in the functions and labels of the buttons B1-B5. The changes largely optimized efficiency and the functionalities required by those screens. An example of such case is with the Add New User screen. On the original low-fidelity model, the up and down arrows were meant to provide both forward and backward scrolling in the process of selecting a character at the cursor. Then, after usability testing, the means to cancel or go back was needed. Thus bidirectional scrolling became unidirectional to free up one function button for the cancel option. Also, since there are also the left and right arrows (for cursor movement) on the same screen, labeling the character scroller as up and down arrows could be misleading. Therefore the character scroller was labeled “ABC..” instead.


Originally there were seven buttons on the scale interface, all placed at the bottom side of the LCD. To provide grouping and more space between the B buttons for better labeling and larger font size, the Menu and Read buttons were moved to the left side of the LCD. Also, the Help button was added next to Menu and Read. The additional Help button offers directions for interacting with the current screen or explains the listed items in better detail. Every screen comes with its own guide–it pops up on the scale LCD and goes away at the press of a button.



Usability Testing




Usability testing was done on computers in quiet rooms in home settings. The participants were asked to imagine that the top portion of the screen is what they see on the actual scale, and that the two buttons at the bottom are only there merely to simulate the act of stepping on and off the physical scale. Participants were told that the study is not on them but on the scale design and functionality. They received description of the tasks they were to perform and were asked to sign the consent form. Next, they proceeded to fill out the pre-test questionnaire. Then they were left alone to carry out the tasks given by interacting with the program. Afterward the participants evaluated the system through the post-test questionnaire. On average each session took approximately 15-20 minutes.





Participants were asked to test ScalePlus based on the following scenarios.



Your name is Bob, a good friend of a family with a ScalePlus. You came over for dinner and afterward you saw the scale and want to weigh yourself. Press "Simulate user stepping on ScalePlus" and choose "unknown" from the list because the scale does not recognize Bob as a user.



You are the scale owner. After weighing himself and hearing that the scale could keep track of his weight, Bob asked you to add him on. On the scale you press Menu ->B3->B1. For this task, pressing B5 would add Bob on as a new user of the scale.



You are Bob. After the owner created an account for you on the scale, you rush on to try it out. Press "Simulate user stepping on ScalePlus" and choose Bob from the user drop down box (and fill out other fields) to simulate the scale recognizing you as a user.



You are Alex. Seeing Bob on the scale, you wonder when the last time you weighted yourself was. You also forgot what your previous weight was. You decide to step on the scale to find out.





Mrs. J is a 53 year old woman who weighs herself once every few days and often memorizes the reading from one time to another. Mrs. J knows very basic computer skills and only uses the computer for word processing. She didn’t have problems with font size on the screen, but it took her time to read the screens and follow instructions to complete the tasks. If having a choice, she prefers ScalePlus over the typical bathroom scale.


Mr. K is a 26 year old guy who is a regular and enthusiastic computer user. He intuitively browsed between screens and completed all tasks with speed and ease. He even tried selecting other functions on the scale interface and was disappointed to find them not doing anything (because those are not implemented yet). He pointed out that there should be a means for providing help when something on the screen is not obvious to the user. Mr. K rarely weighs himself and has no interest in owning ScalePlus or any bathroom scale.


Mr. L is a 25 year old student at UMUC. He is slim built and only weighs himself about once a month. He is relatively experienced with computers running Windows. Getting through the tasks wasn’t a problem. Mr. L mentioned that the history recall feature is pretty nice. He would use it if it’s there but he is not willing to go out and buy one because of the feature. Furthermore he pointed out that though the record keeping feature is nice, it does not motivate him to use ScalePlus more often than the regular scale.


Additionally, 5 usability tests were given to the younger group, ages 5, 10, 10, 14, 14. All 5 participants were females and had little or no knowledge about computers. They had only interacted with computers through chatting sessions and doing online research for school. The test was run under the same environment for all 5 participants, in a quiet room. The answers to the pre and post-test questionnaire depended on the age groups that were being tested.


Age group 14: Both participants were 14 year old female high school students. For this age group it took each about 10 minutes to finish the task with minimal questions. Both girls care about their weight but one was willing to use ScalePlus more than the other. After a short discussion with the girl that did not really see herself using ScalePlus, it was apparent that English was the problem. The girl’s first language was not English so it was hard for her to follow the instructions and fill out the paperwork. The other girl really liked ScalePlus and she could see herself using it more than twice weekly to keep track of her weight and body fat. Another feature that they liked was that they could eventually monitor their weight on a graph or export it to text. Both girls would like to see diet advice added into ScalePlus. For this age group the scale was appropriate and simple to use, but one problem was that two users could not be registered under the same name.


Age group 10: This age group was very interesting. The two girls were able to accomplish the goals when the instructions were read aloud to them instead of having to concentrate on the current task and reading at the same time. The girls were asked to repeat the tasks a few times to see if it would be easier if they already knew exactly what to do. After 5 to 6 times repeating the tasks the girls were having fun and seemed more interested in keeping track of their weight using ScalePlus. It took them about 30 minutes each to get comfortable with the interface and tasks. There were also a few problems in this age group. The first problem was that it took the participants more time to learn how to operate the scale. The terms were more appropriate to the 14 year olds but they were too advanced the 10 year olds. The final problem was that there were no back, cancel or help buttons that could help them out. Both girls asked several times how to start over and how to undo an action.


Age group 5:  It was surprising to find that the 5 year old was able to follow the instructions as well as the 10 year old group after a few tries. It took her a long time but she eventually finished all the tasks. After about an hour it was easy for her to navigate the scale. She was very persistent in getting it to work even if it meant to start over every time. It was hard to relay what problems she faced, but she was able to do the weight part. Like the other girls, the 5 year old thought that ScalePlus was very exciting to use to keep track of her weight.





Age is a factor that determines if users are likely to understand what to do with ScalePlus. Some of the tasks given are better suited for users who are able to follow instructions on how to setup ScalePlus. Children and young users are not fit to carry out those tasks. As users of ScalePlus their interactions with the scale would likely be simply stepping on and read numbers.


In the area of effectiveness of ScalePlus as a household device, many preferred to use ScalePlus over ordinary bathroom scale. However, a few showed lack of interest in owning ScalePlus. Survey results seem to explain this phenomenon. It seems to be common that those who weigh themselves regularly have interest in ScalePlus and are willing to weigh themselves more often. On the other hand, to the people who do not weigh themselves regularly the extra functionalities offered by ScalePlus still are not appealing enough to change their minds.


Below is a brief table of identified problems and their ranking (on a scale of 1 to 5) in terms of importance and effort to resolve, where 1 is the least important or easiest to resolve and 5 is the most important or hardest to resolve.



Possible Solution



Users cannot have same name

Add number as suffix



Means for Help/Cancel/Back

To be handled during further implementation of the system