Question

The instructor of an English course is interested in knowing if there is a difference in the mean grades between the Peterborough and Oshawa classes. Summary data for these classes are as follows:

Ptbo Class Osh Class

Mean 73.00 67.00

N   101 61

SD 10.50. 11.00

Is there a significant difference in the average grades of these two classes?

Compute the power of the findings, explaining what it means (7 grades)

What is the effect size? Interpret the effect size

Answer 1

From above test, we see that P-value>0.05 so we can assume two population variances are same.

where mu(1)=true mean grade of Peterborough class; mu(2)=true mean grade of Oshawa class.

Power of the findings=P-value=0.001 i.e. probability of obtaining values as extreme as the observed values i.e. 3.46, assuming that the null hypothesis is correct. We know if P-value<0.05 then we reject null hypothesis at 5% level of significance. Here since P-value=0.001<0.05, there is significant difference in the mean grades between the Peterborough and Oshawa classes.