PROBLEMS: (Show 5 step process) 1. Independent random samples taken on two university campuses revealed the following information concerning the average amount of money spent on textbooks during the fall semester. University A University B Sample Size 50 40 Average Purchase $280 $250 Standard Deviation $20 $23 At = .05, test to determine if, on the average, students at University A spend more on textbooks then the students at University B.

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## Answers ( 1 )

t- test for difference ofmeansStep:1.Null hypothesis(H_{o}) : (i.e.,the average amount of money spent ontextbooks during the fall semester is same.)Step:2.Alternative hypothesis(H_{1}) :Step;3. Test statistic is given by

Therefore, Z cal .value=30.3821

Step:4 For a one tailed test ,the critical valueof Z at 5%l.o.s. is 1.645 .The criticalregion for left-tailed test thus consists of all values of Z islessthan or equal to

1. 645

Step:5.

Here Z cal .value is greater than the Z tab. value .Hencewe reject null hypothesis.Hence, on the average, studentsat University A spend more on textbooks then the students atUniversityB.