After careful ethical review of planned procedures, a researcher tests a new brain activation drug by taking a sample of 50 volunteers and randomly assigning 25 participants to the treatment condition and 25 to the control (placebo)condition.She then carries out an fMRI scan to assess the level of activation in regions of the participants' brains 30 minutes after administering the drug.She carries out a between-participants t-test in SPSS which provides the output shown below: What further advice is appropriate to give the researcher here?
A)The variances look as if they could be unequal.
B)It is worth ensuring that the distributions of the scores are normal.
C)The negative confidence interval suggests she needs to reduce statistical uncertainty further.
D)The t-test should be accompanied with a measure of effect size such as Cohen's d.
E)Both (a)and (d).

Question

After careful ethical review of planned procedures, a researcher tests a new brain activation drug by taking a sample of 50 volunteers and randomly assigning 25 participants to the treatment condition and 25 to the control (placebo)condition.She then carries out an fMRI scan to assess the level of activation in regions of the participants' brains 30 minutes after administering the drug.She carries out a between-participants t-test in SPSS which provides the output shown below:  What further advice is appropriate to give the researcher here?
A)The variances look as if they could be unequal. 
B)It is worth ensuring that the distributions of the scores are normal. 
C)The negative confidence interval suggests she needs to reduce statistical uncertainty further. 
D)The t-test should be accompanied with a measure of effect size such as Cohen's d. 
E)Both (a)and (d).

Quizplus · Accepted Answer

The output suggests that the variances could be unequal, so it is appropriate to give the researcher advice to check for this assumption. Additionally, the researcher should include a measure of effect size such as Cohen's d to provide a more complete understanding of the magnitude of the difference between conditions. Therefore, choice E is the best answer. Option B does not seem to be an issue here since the sample size is large enough to assume normality through the Central Limit Theorem. The negative confidence interval does not suggest that the researcher needs to reduce statistical uncertainty further, as it only expresses a range of values that the true mean difference could take with a certain level of confidence.

After Careful Ethical Review of Planned Procedures, a Researcher Tests