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Viewing Spending Categories
Learnability
Actions are clearly visible and derive from known smartphone menus. The design is also very intuitive.
Visibility
This design is very visible. Most menus have only a few buttons, and they are located in the center of the screen. The affordances of some of the actions are not very clear, as it is not clear which options are editable, and which type of input is required for each field.
Efficacy
The design is very efficient, using the minimal amount of menus and screens to input a receipt. Also, when presenting expenses across different categories, the interface shows the user all the relevant information in one graph, saving him a step of typing a specific query.
Error Prevention
This design allows easy error prevention using the "retake" button. With just one click, the user can recover from an error. Also, re-editing a receipt after it was inputted is pretty easy and straight-forward.
Design 2
Learnability
Most of the options of this design are derived from existing designs of many common smartphone menus. Taking a picture of a receipt and browsing through old receipts is similar to the iPhone's camera interface, and entering and editing receipt and report details are similar to its settings menu. This aspect of the design makes it very learnable for smartphone users. The other elements that do not have a parallel in common menus or applications are sufficiently documented, with the buttons stating exactly which action should be taken. One aspect in which the user will have trouble learning the interface is navigating between the different screens. It is not always clear which button will lead to which screen and which receipt/report the user is currently looking at.
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This design does not prevent the user from making most errors. The different fields in the receipt categories do limit the types of input a user can insert, but common mistakes will probably include mis-categorizing a receipt, entering the wrong amount, or attaching the wrong picture to the receipt. Mis-categorizing a receipt or entering the wrong amount can be fixed be fixed by looking up the receipt item under the report and editing it, but attaching the wrong picture would force the user to delete the receipt entirely and create a new one.
Design 3
Learnability
Since this design takes most of the input from the receipt, it minimizes the input it requires from the user and thereby makes learning how to use it fairly easy. The different menus derive from similar known menus, and therefore most smartphone users will find it very easy to use the interface.
Visibility
This design has pretty good visibility. It minimizes the number of editable options and buttons the user will need, and the buttons that are included in the design are large and in the center of the screen. The different actions have appropriate affordances, and it is easy to find the relevant controls in every screen.
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While this design increases user efficacy by automatically detecting most receipt details on its own, some other elements of the design do compromise efficacy. The scan screen is shown with only one option, forcing the user to make an unnecessary selection.
Error Prevention
Error prevention is the biggest weakness of this design. Since it is highly automated, if the user encounters errors in entering a receipt, or even if the system analyses the receipt wrongly, it would be very hard to recover from the error. The user have no easy way to override the fields.