Question

A major retail clothing store is interested in estimating the difference in mean monthly purchases by customers who use the store's in-house credit card versus using a Visa, Mastercard, or one of the other major credit cards. To do this, it has randomly selected a sample of customers who have made one or more purchases with each of the types of credit cards. The following represents the results of the sampling:

In House Credit Card National Credit

Card Sample Size 86 113

Sample Mean $45.67 $39.87

Sample Standard Deviation $10.90 $12.47

Suppose that the managers wished to test whether there is a statistical difference in the mean monthly purchases by customers using the two types of credit cards, using a significance level of .05, what is the value of the test statistic assuming the variances are equal?

t = 3.43

z = 11.91

z = 3.51

t = 2.86

Answer 1

The pooled estimator of the sample variance                                  
  
The pooled estimator of the sample standard deviation=   11.82      
                                  
T test formula for mean difference.(Variances unknown and equal)                                  


=3.43     

Therefore, t=3.43