2 different metric types
observable + quantifiable
3 common questions with metrics
3 general metrics names
Performance Metrics
Issue-Based Metrics
Self-Reported Metrics
9 performance metrics names
1 combined metric name
Single usability metric
3 self-reported metric names
1 issue-based metric name
Usability problems
Performance metrics (there ae six of them)
Effectiveness formula explanation
Effectiveness formula
(Number of tasks completed/Total number of tasks) X 100%
Effectiveness example. 5 tasks and a user completes 3 of them.
3/5 X 100% = 60%
3 Levels of success
Complete Success
Partial Success
Failure
How to resolve a task when a user is not successful
Tell the users at the beginning of the session that they should continue to work on each task until they either complete it or reach the point at which, in the real world, they would give up or seek assistance (from technical support, a colleague, etc.).
Time on task explanation
Time on task (sometimes referred to as task completion time or simply task time).
Caveat: Sometimes, slower is better
Ex: They are truly engaging with the website
4 steps to make efficiency quantible
Lostness formula
N: # of DIFFERENT webpages visited
S: total # of webpages (duplicate included)
R: minimum # of pages required to visit
L = sqrt(N/S-1)^2 +(R/N-1)^2
2 types of rating scales
likert and semantic differential scales
4 types of self-reported metrics
Likert scale definition
5 point rating scale following:
1. Strongly disagree
2. Disagree
3. Neither agree nor disagree
4. Agree
5. Strongly agree
Semantic Differential scales definition
Will have a scale with two values on each side. These two values will be opposites such as: weak and strong, ugly and beautiful, cool and warm. example below
weak o o o o o o o strong
SUS meaning and definition
System Usability Scale - consists of a 10 item easy questionnaire with five response options for respondents; from Strongly agree to Strongly disagree
10 questions used in SUS
CSUQ meaning and definition
Computer System Usability Questionnaire - has 19 questions about usability; from strongly disagree to strongly agree
3 severity ratings
low, medium, high