Usability Evaluation with Users CMPT 281

Transcription

1 Usability Evaluation with Users CMPT 281

2 Outline Usability review Observational methods Interview methods Questionnaire methods

3 Usability ISO : The extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency, and satisfaction, in a specified context of use Efficiency Effectiveness Satisfaction Context: user, task, environment

4 Nielsen s model of usability

5 Operationalizing usability How to assess usability criteria? What measures? What thresholds? What is usable enough?

6 Observational Evaluation Methods

7 Observational Methods Simple observation Think-aloud protocols Retrospective think-aloud protocols Co-discovery learning Recording observations

8 Simple Observation User is given a task, and evaluator just watches the user Problem: no insight into the user s decision process or attitude

9 Think-aloud Protocol Subjects are asked to say what they are thinking/doing: What they believe is happening What they are trying to do Why they took an action Gives insight into what the user is thinking

10 Think-aloud Protocol Problems: Awkward/uncomfortable for subject (thinking aloud is not normal!) Thinking about it may alter the way people perform their task Hard to talk when they are concentrating on problem Still the most widely used method in industry

11 Other Problems with Think-aloud

12 Retrospective Think-aloud Problems with Think-aloud: Awkward for subject (thinking aloud not normal!) Thinking about it may alter the way people perform their task Hard to talk when they are concentrating on problem Solution: videotape the experience, perform a retrospective think-aloud Has its own problems Awkwardness of watching themselves on video Awkwardness of reliving mistakes Reflection of the experience rather than in context 12

13 Co-discovery Learning Two people work together on a task Normal conversation between the two users is monitored Removes awkwardness of think-aloud, more natural Provides insights into thinking process of both users 13

14 Field Studies Observe in the field = natural environment Sit and observe Video records Join the culture (ethnography)

15 Field Studies Observe in the field = natural environment Sit and observe Video records Join the culture (ethnography) Requires that the system be fully deployed Highest degree of realism Can be highly specific to the particular setting Can take a long time

16 Recording Observations Paper and pencil primitive but cheap evaluators record events, interpretations, and extraneous observations evaluator seems disengaged problem: writing is slow prepared coding schemes can help; just tick off events Audio recording capture discussion (think aloud, co-discovery) hard to synchronize streams (e.g., interface actions) (expensive) tools exist to help transcription is slow and difficult! tools exist to help

17 Recording Observations Video recording can see what a user is doing (good to use one camera/scan converter for screen + one for subject) can be intrusive (at least initially) analysis can be challenging annotation is time consuming and dull Companies often build usability labs with one-way mirrors, video cams, etc.

18 Analyzing Observation Data Qualitative data: interpreted to tell a story Qualitative data: categorized Quantitative data: presented as values, tables, charts, and graphs often treated with statistical tests How do you know which analysis is appropriate? Depends on what you are using it for

19 Interviews

20 Querying Users with Interviews conversations with a purpose excellent for pursuing specific issues more interactive than observation: address specific issues of interest more flexible than questionnaires: probe more deeply on interesting issues as they arise problems accounts are subjective time consuming (to conduct and to analyze) evaluator can bias the interview prone to rationalization of events/thoughts by user user s reconstruction may be wrong

21 Planning the Interview general what is the purpose of the interview? how many people? (breadth vs. depth) length of interview & number of sessions scheduling interviews (location, times, people) will the interview be recorded? (audio, video; transcription) avoid: asking long questions using compound sentences using jargon asking leading questions and generally be alert to unconscious biases.

22 Interviews three main types: 1. open-ended / unstructured 2. semi-structured 3. structured control & pre-determined questions other categories (can include types above): 4. group 5. retrospective

23 Unstructured Interviews most like a conversation, often go into depth open questions exploratory key is to listen rather than talk: practice silence! pros/cons: + rich data, things interviewer may not have considered - easy to go off the rails - time-consuming & difficult to analyze - impossible to replicate

24 Structured Interviews predetermined questions (like questionnaire, often with a flowchart) closed questions short, clearly worded questions confirmatory pros/cons: + replicable - potentially important detail can be lost better (cheaper) with a questionnaire?

25 Semi-structured Interviews Between structured & unstructured Uses elements of both In usability studies, unstructured and semistructured are the most common

26 Group Interviews (Focus Group) 3 10 people interviewed at one time usually has agenda, but may be structured/unstructured skilled moderator critical! usually recorded pros/cons: + can accommodate diverse and sensitive issues + opinions developed within a social context + good way to locate proto-users : most articulate, imaginative participants can help later w/participatory design - some interviewees may dominate - expensive: usually pay participants + professional moderator - people may not know what they think (or be afraid to express it)!

27 Retrospective Interview post-test interview to clarify events that occurred during system use: record what happened, replay it, and ask about it pros/cons: + excellent for grounding a post-test interview + avoids erroneous reconstruction + users often offer concrete suggestions - requires a second session I didn t see it. Why don t you make it look like a button? Do you know why you never tried that option?

28 Overview of an Exploratory Interview 1. explain purpose of the interview allow time to get acquainted with the interviewee provide understanding and background 2. enumerate activities find out what the user does 3. explain work methods find out how the user does things (skills and knowledge) 4. trace interconnections determine other people and activities that are related 5. identify performance issues explore current problems and impediments to success

29 Things You Uncover during Interviews exceptions lots of things people do are not in the manual many jobs evolve to fit changing circumstances much of this is not documented many times management does not know about this domain knowledge most people know a lot about their jobs, and those they work with terminology, common phrases, specific details audio recording helps capture this video recording helps provide body language written notes can provide context, but not always details

30 Questionnaires (Surveys)

31 Querying Users with Questionnaires closed or open questions get evidence of wide general opinion or experiences after an experiment pros/cons: + preparation expensive, but administration cheap can reach a wide subject group (e.g. mail or ) + does not require presence of evaluator + results can be quantified - risk: low response rate and/or low quality responses

32 Questionnaires: Designing Questions establish the purpose of the questionnaire: what information is sought? how would you analyze the results? what would you do with your analysis? determine the audience you want to reach typical: random sample of between 50 and 1000 users of the product -- why a random sample? test everything before sending it out: test the wording test the timing test the validity test the analysis

33 Administering Questionnaires in-person administration take home (conventional) requires time to administer, but highest completion rate often subjects don t complete / return the questionnaire permits subjects to answer on their own time responses may tend to be more free-form attachments may be a problem response rates depend on trust in source web-based forms general issues standardize formats and responses scripts to ensure correct / complete payment or incentives anonymity self-selection

34 Styles of Questions: Open-ended asks for opinions good for general subjective information but difficult to analyze rigorously E.g., can you suggest any improvements to the interface?

35 Styles of Questions: Closed restricts responses by supplying the choices for answers can be easily analyzed but can still be hard to interpret, if questions / responses not well designed! alternative answers should be very specific Do you use computers at work: O often O sometimes O rarely In your typical work day, do you use computers: O over 4 hrs a day O between 2 and 4 hrs daily O between 1 and 2 hrs daily O less than 1 hr a day

36 Styles of Questions: Scalar - Likert Scale measure opinions, attitudes, and beliefs ask user to judge a specific statement on a numeric scale scale usually corresponds to agreement or disagreement with a statement Characters on the computer screen are hard to read: strongly agree strongly disagree

37 Styles of Questions: Scalar - Semantic Differential Scale explore a range of bipolar attitudes about a particular item each pair of attitudes is represented as a pair of adjectives WebCT is: clear confusing attractive ugly

38 Styles of Questions: Multi-Choice respondent offered a choice of explicit responses How do you most often get help with the system? (tick one) O on-line manual O paper manual O ask a colleague Which types of software have you used? (tick all that apply) O word processor O data base O spreadsheet O compiler

39 Styles of Questions: Ranked respondent places an ordering on items in a list useful to indicate a user s preferences forced choice Rank the usefulness of these methods of issuing a command (1 most useful, 2 next most useful..., 0 if not used) 2 command line 1 menu selection 3 control key accelerator

40 Styles of Questions: Combining Open-ended & Closed Questions gets specific response, but allows room for user s opinion It is easy to recover from mistakes: disagree agree comment: the undo facility is great!

41 Herman Miller Aeron Chair Comfort Likert 1-10 (want 7.5) Got 4.5 Eventually inched up to 8 before release Aesthetics Likert 1-10 Got 2-3 (never above 6!) Usually a relationship between these two but it didn t happen! Focus Group Check on pricing Architects and designers liked Facility managers and ergonomicists hated! Entire design was *actually* user friendly Where is this chair at today?

42 Considerations Style of Questions Open Ended Closed Choose one Choose all that apply Ratings (scale) Rankings Ease of Analysis Poor Depends Easy Somewhat easy* Easy Somewhat easy *Note: Can t really make a pie chart if the responses don t add up to 100%

43 Be Considerate of Your Respondents not just because it s nice, but it works better. questionnaire length (short is good): think in terms of reasonable completion times do not ask questions whose answers you will not use! privacy invasions: be careful how / what you ask motivation why should the respondent bother? usually need to offer something in return but be careful about introducing bias.

44 Deployment Issues Online/ html tools U of S survey tool Survey Monkey Choice impacts ease of analysis responses? Go directly to database

45 Presenting questionnaire results Choose one

46 Presenting questionnaire results Choose one Choose all that apply

47 Summary: Questionnaires 1. Establish purpose 2. Determine audience 3. Variety of administration methods (for different audiences) 4. Design questions: many kinds, depend on what you want to learn 5. Be considerate of your respondents 6. Motivate your respondents (without biasing them).