13. The average final grade in a larger physics class has consistently been 74%

Question

13. The average final grade in a larger physics class has consistently been 74% over the past several years. The professor decided to incorporate different activities into the course this past semester and is curious if the higher engagement during class led to a higher class average. This semester, the final grades for the 123 students enrolled in his class averaged 77% with a standard deviation of 11%. What is the level of evidence that the professor's experiment in the classroom worked? a. 0.0012 b.0.0014 c. 0.9986 d. 0.9988

Explanation / Answer

The average grade before treatment=X1=0.74

The average grade after treatment=X2=0.77

sample size n=123

sample standard deviation S=0.11

difference between two means=d=X2-X1=0.77-0.74=0.03

t-statistic= d/(S/sqrt(n))= 0.03/(0.11/sqrt(123))=3.02469

correspnding p value with 122 degrees of freedom=1-pt(3.02469,df=122)=0.0014

so the correct answer is b

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