Question

Independent Samples T-TEST

Two rival schools, West Ridge College and East Ridge College, each claim to have a better microbiology program than the other.  The microbiology students at both schools take the same national exam at the end of the year.  Although West Ridge College gets a higher mean score, the East Ridge College’s microbiology professor claims that the difference in scores is too small to be statistically significant.  Here is the data

West Ridge College:  Mean or   = 85.8;  12.8;  = 16

East Ridge College:  Mean or   = 77.5;  13.4;   = 16

• (a) What are and ?
• (b) What is the pooled variance?
• (c) What is the tcrit?
• (d) With Two-tailed Alpha = .05 what is the tcrit?
• (e) Please write a summary of the results.  Remember to mention the sample, the conditions of the independent variable, and the dependent variable.
• (f) What is Cohen’s d for this study?

Answer 1

Ans:

a)

b)

pooled variance=((16-1)*12.8^2+(16-1)*13.4^2)/(16+16-2)=171.7

c)

standard error for difference=SQRT(171.7)*SQRT(2/16)=4.633

Test statistic:

t=(85.8-77.5)/4.633

t=1.791

d)df=16+16-2=30

critical t value(two tailed)=tinv(0.05,30)=+/-2.042

e)Fail to reject the null hypothesis.

There is not sufficient evidence to conclude that there is a significant difference in the the scores.

(difference is scores is not statistically significant)

f)

Cohen's d=(85.8-77.5)/sqrt(171.7)=0.633