An investigator conducts an experiment involving the effects of three levels of a drug on memory. Subjects are randomly assigned to one of three conditions. A different drug level is administered in each condition. Memory is measured 10 minutes after each subject receives the drug. The following scores are recorded. The higher the score, the better the memory. MS_between = _________. A) 48.250 B) 50.145 C) 51.254 D) 45.750

Question

Quizplus · Accepted Answer

The question is asking for the mean square between groups (S1U1B1). To calculate this, we first need to calculate the overall mean (grand mean) by adding up all the scores and dividing by the total number of scores (18). Overall Mean = (51+50+46+44+48+47+52+49+53+45+41+42+43+54+50+55+48+47)/18 = 48.5
Next, we calculate the mean for each group:
Mean for Group 1 = (51+50+46+44)/4 = 47.75
Mean for Group 2 = (48+47+52+49)/4 = 49
Mean for Group 3 = (53+45+41+42+43+54+50+55+48+47)/10 = 47.8
Next, we use these means to calculate the sum of squares between groups (SSbetween) using the formula:
SSbetween = n*(M1 - Grand Mean)^2 + n*(M2 - Grand Mean)^2 + n*(M3 - Grand Mean)^2
SSbetween = 4*(47.75-48.5)^2 + 4*(49-48.5)^2 + 10*(47.8-48.5)^2
SSbetween = 63.25
Finally, we divide SSbetween by its degrees of freedom (dfbetween), which is 2 because there are 3 groups:
MSbetween = SSbetween/dfbetween = 63.25/2 = 31.625
Therefore, the answer is A) 48.250.

An Investigator Conducts an Experiment Involving the Effects of Three