1) A sports nutritionist is interested in determining whether athletes drink more water on days when they weight lift or days when they do cardio. She records the number of water bottles five athletes drink on both a weight lifting and a cardio day. Does the exercise type influence water consumption?
| Weight Lifting | Cardio | |
| Athlete 1 | 6 | 8 |
| Athlete 2 | 7 | 9 |
| Athlete 3 | 5 | 5 |
| Athlete 4 | 8 | 8 |
| Athlete 5 | 9 | 8 |
Video solution to problem
slides for dependent samples t test demo 1
2) A student is interested in learning whether having a TV on in the background influences learning while studying compared to having nothing in the background. She collects the scores from six students when they study with a TV, and also when they study with no TV. Does having the TV on influence learning?
| TV | No TV | |
| Student 1 | 72 | 84 |
| Student 2 | 78 | 82 |
| Student 3 | 63 | 94 |
| Student 4 | 74 | 84 |
| Student 5 | 92 | 98 |
| Student 6 | 76 | 88 |
Video solution to problem
slides for dependent samples t test demo 2
Answers
1) People drink the same amount of water whether they do cardio (M = 7.6, SD = 1.52) or weight lift (M = 7, SD = 1.58) (t (4) = -1, p > 0.05, Cohen’s d= -0.45).
2) People learn more with the TV off (M = 88.33, SD = 6.37) than the TV on (M = 75.8, SD = 9.47) (t (5) = -3.20, p < 0.05, Cohen’s d= 1.31).
More videos demonstrating hand calculations
More practice problems
http://www.cliffsnotes.com/math/statistics/univariate-inferential-tests/paired-difference-t-test
http://www2.webster.edu/~woolflm/ttest.html – you will need to know when to use an independent vs dependent samples t-test