Problem Population A- Mean of 117 and SD of 5 Population B- Mean of 125 and SD o

Question

Problem

Population A- Mean of 117 and SD of 5

Population B- Mean of 125 and SD of 7

****Construct a 90% confidence interval for the mean difference when individual samples of 75 are taken out of each population.

Is this correct?

1) Confidence coefficiant should be found via z table not t table because the sample size is so large. Because of this, the confidence coefficiant is 1.645.

2) 7^2=49 and 5^2= 25 and Fstat= 49/25= 1.96 and Fcrit=1.47 so because 1.96>1.47 the variances are not considered equal

3) because variances are not equal I set up my equation as such:

IF I AM INCORRECT CAN YOU PLEASE TELL ME WHY?

THANK YOU!

Explanation / Answer

Answer to the question is right:

1. Yes ,you would have used the t-tables if n<30

2. Fcrit<Fstat, then reject Ho, and 'accept' alternate hypothesis that the variances are unequal. - even this is correct

3. Z = 1.645, and the formula used is right, so the 90% interval is correct

So, your answer is right

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