An educational psychologist wanted to investigate whether a new spaced-repetition mobile application improves daily kanji (Japanese characters) retention in language learners. They posted an invitation to participate on a popular online Japanese language learning forum and recruited a volunteer sample of 12 participants.
During Week 1, participants studied Japanese characters using their normal methods and completed a daily recognition test (scores out of 50). During Week 2, participants used the spaced-repetition mobile application for 20 minutes daily and completed a similar daily recognition test.
The data collected (mean scores for each participant) is presented below:
| Participant | Week 1: Normal methods (Mean score) | Week 2: Mobile application (Mean score) |
|---|---|---|
| A | 31 | 38 |
| B | 24 | 29 |
| C | 40 | 41 |
| D | 18 | 26 |
| E | 33 | 35 |
| F | 27 | 34 |
| G | 45 | 44 |
| H | 29 | 36 |
| I | 35 | 39 |
| J | 22 | 31 |
| K | 38 | 40 |
| L | 15 | 24 |
Outline one way that the sampling technique used to obtain participants for this study could have affected the generalisability of the results.
