iScale: Studying Long-Term Experiences through Memory - Modeling Users' Experiences with Interactive Systems - page 103

of how one's experience with a product developed over time. As a measure of the
test-retest consistency of the graphs, we computed the area between the two graphs
through sampling them in 100 steps (see figure 5.9).

5.4.2 Analysis and Results

A total of 457 experience reports were elicited. Participants provided an average
of 4 to 6 experience reports depending on the recall condition. Ninety-five percent
of all experiences were related to the first six months of use. We compare the two
graphing tools to the no-graphing (control) condition in terms of a) the number of
elicited experience reports, b) the richness of elicited experience reports, c) the test-
retest consistency in time estimation, and d) the test-retest consistency of graphs.

5.4.2.1 Number of Elicited Experience Reports

Figure 5.7 shows the number of reported experiences as a function of the mode of
recall. An average of 6.1 experience reports was elicited when using the constructive
iScale, 4.6 when using the value-account iScale, and 4 when using the no-graphing
(control) tool.
An analysis of variance with number of experience reports as dependent vari-
able and mode of recall (constructive, value-account, control), and product quality
(ease-of-use, innovativeness) as independent variables revealed a significant main

8

6

4

2

0

constructive value-account control

Mode of recall

Fig. 5.7 Average number of experience reports, together with their 95% confidence inter-
vals, elicited by participants using the constructive, the value-account, and the no-graphing
(control) version of iScale.