Question

16. (7pts) A researcher presented the findings of a study at a local conference. In the study, the researcher investigated the impact of heat stress on the performance of test-takers. She hypothesized that test-takers exposed to high levels of heat in a temperature- controlled room would make significantly more errors compared to test-takers in a standard-temperature temperature-controlled room. Prior to hypothesis testing, the researcher conducted a power analysis and found that she needed 46 participants to have sufficient power. At the conference, the researcher reported the following results: t(44) = 2.33, p < 0.05, Cohen's d = 0.9. The researcher was quite confident in her findings and concluded that temperature affects test-taking performance and that the effect should be factored into scoring exams. Another researcher at the conference criticized the researcher's results, citing another study that found evidence to the contrary. How could the original researcher defend her results?

17. (8pts) A researcher was interested to know whether there are differences in life satisfaction between older adults and younger adults. Ten older adults (over the age of 70) and 10 younger adults (between 20 and 30) were given a life satisfaction test. Scores on the measure ranged from 0 to 60 with high scores indicating high life satisfaction. The researcher found a statistically significant difference between the average life satisfaction of the two groups: that for the older adults was 44.5 (SD = 8.68), while that for the younger adults was 28.2 (SD = 8.66), t(18) = 4.20, p < 0.05. Calculate the size of this effect, and then use Cohen's conventions to interpret its size.

Answer 1

From the given information,

The null hypothesis is the hypothesis of no difference, for the given problem the null hypothesis is,

Null Hypothesis-: The heat exposed to the test takers in the temperature controlled room and standard temperature controlled room is the same.

Alternative Hypothesis-:The heat exposed to the test takers in the temperature controlled room and standard temperature controlled room are not same.

The value is less than 0.05 which means that that there is not enough evidence to reject the alternative hypothesis, so reject the null hypothesis and it is concluded that the heat exposed to the test takers in the temperature controlled room and standard temperature controlled room are not same and the temperature affects the test taking performances.

The Cohen's D value is 0.9 which indicates that the affect of temperature is large and it should be factored into scoring exams.

For the life satisfaction of younger and older adults, the degrees of freedom is 18 and the value of t test is 4.20.

The Cohen's D size formula is given by,

Substitute 4.20 for and 18 for d.f in the above mentioned formula.

This indicate large effect size.