Question

A researcher conducts a single-sample t test and finds statistical significance at the 0.01 level. The effect size is then calculated and found to be 0.50. What might you conclude about the findings?

A. These findings are exciting because statistical significance was found with a very small effect, indicating that the results are real and the chance of a Type I error are low.

B. While the results of the test are statistically significant, the effect size indicates that they may not be practically significant. It might be the case that a very large sample was studied, driving up the test statistic value.

C. The findings seem flawed because without a substantial effect size, it is not possible to find statistical significance.

D. The results are both statistically and practically significant in this case, as the effect size indicates a medium effect, and the 0.01 level of significance is rather impressive.

B is incorrect. Please explain why the new answer is correct, I don't understand.

Answer 1

D. The results are both statistically and practically significant in this case, as the effect size indicates a medium effect, and the 0.01 level of significance is rather impressive.

D option

Cohen suggested that d=0.2 be considered a 'small' effect size, 0.5 represents a 'medium' effect sizeand 0.8 a 'large' effect size. This means that if two groups' means don't differ by 0.2 standard deviations or more, the difference is trivial, even if it is statistically signficant.

So, effect size is of medium effect

Thus, option D