Choose the Proper Screen-Based Controls 545

Step 7: Choose the Proper Screen-Based Controls 545

4. Radio buttons

5. Menus (drop-down list boxes)

Entry

6. One entry area

7. Four entry areas The direct manipulation methods reflected the perceived strength of graphical sys-

tems, namely, manipulation of objects on the screen. The selection methods utilized indirect manipulation and illustrated the types of controls available in graphical screen design. The entry methods are a carryover from text-based screens, the only way the task could be accomplished for many years. Study participants were experi- enced Microsoft Windows users. No instructions were provided on how to carry out the item reorganization tasks. Users had to rely on their experience.

The two fastest methods were radio buttons and the one entry field. The methods most preferred by participants were radio buttons, drop-down list boxes, and one entry field. The direct manipulation methods fared rather poorly, ending midlist in the speed and preference rankings. The surprise, perhaps, was the good showing of an old control: the one entry field, or text box.

Tullis (1993) performed a follow-up to this study by asking a group of programmers to predict the study results (without, of course, being privy to its results). For both reordering speeds and subjective preferences, their predictions were way off the mark. They anticipated that the direct manipulation methods would be the fastest and most preferred. This, of course, was not at all the case. They predicted that radio buttons would be midway in the speed and preference ordering and that one entry field would

be near the bottom. Again, they were quite mistaken. The correlation between their predictions and actual reordering speed was a dismal .07. They did slightly better on predicting preferences, the correlation being .31.

Based on these studies, Tullis concludes that control selection decisions made according to convention and intuition may not necessarily yield the best results. This conclusion might be modified to say, with a great deal of justification, that such deci- sions made using common sense may not even yield good results. Just because a control or process is new does not necessarily make it better. Just because the control has been around a long time does not necessarily make it poorer. Controls should be selected on the basis of the objectives they are to achieve, and they should be subjected to the same rigorous testing as all other parts of the system.

Another control comparison study was conducted by Johnsgard et al. (1995). They evaluated a variety of controls including check boxes, drop-down list boxes, drop- down combination boxes, text boxes, list boxes, radio buttons, sliders, and spin boxes. Speeds, errors, and preferences were obtained for the various controls under various conditions.

546 Part 2: The User Interface Design Process

Table 7.1: Controls Evaluated by Tullis and Kodimer (1992)

DIRECT MANIPULATION

1. Drag and Drop On • The items are arrayed horizontally. An item is dragged to a new location above another item and released. The item in that position moves to the old location of the arriving item.

2. Drag and Drop Between • The items are arrayed horizontally. An item is dragged to a new location between two other items and released. The items are readjusted into new positions, including, when necessary, automatic wrap-around for items located at the end of the line.

SELECTION

3. Icons • The items are arrayed horizontally. Icons are positioned between each pair of items. Selecting an icon switches the positions of each adjacent item.

4. Radio Buttons • The items are presented in a matrix, item name along the left side, item position numbers across the top. Radio buttons in the matrix are selected to represent each item’s position.

5. Menus (Drop-Down List Boxes) • Items are positioned horizontally. A drop-down listing is activated, and the item for that location selected.

ENTRY

6. One Entry Area • A single text entry field is provided. A one-character mnemonic (F,N,S,D) is provided for each choice. The mnemonics are keyed in the order in which the items are to be arrayed.

7. Four Entry Areas • Four text entry fields, labeled with the item names are arranged vertically. A number (1-4) is keyed into each field, indicating the manner in which the items are to be ordered.