# Homework Help: [Statistics] Obtaining test statistic in short problem

1. Jun 26, 2012

### ozill

Hey everyone! Exam practice, that time of year. In this problem 13 with correct answer C, I'm not sure how they get the test statistic: http://i.imgur.com/doar3.jpg

I think they want you to use a F-test, that tests the entire model, which is calculated by: F= ((R^2)/ K)/ ((1 - R^2)/(n-K-1)) where K is the number of independent variables (3 in this question)

Then the R square is the percentage of the model that is explained, so the explained variation in Y / total variation in Y

R^2 = SSR / (SSE+SSR)
SSR= sum of squared regression, SSE=sum of squared errors

Thanks for any help or insight!
Many thanks

2. Jun 27, 2012

### awkward

I think they are doing a contingency table with a chi-square statistic.

3. Jun 28, 2012

### ozill

Right, but I'm still at a loss! :)

4. Jun 28, 2012

### awkward

Well, how many people in each of the three categories would expect, based on the predicted percentages? And how many were actually surveyed?

5. Jun 29, 2012

### ozill

Hey, thanks for helping!

It's a sample of 120 people, so n=120
So in this sample : 60 workers, 30 students, 30 retirees

6. Jul 5, 2012

### Ray Vickson

That was not the question. The question was: how many would you EXPECT in each group if the predicted percentages held true?

RGV