# Chi squared calculations

Hello,

I handed in this problem to my professor and he commented that it is correct except for the chi squared calculations. I have rechecked 4 times and I get the same answer. Do you know what I did wrong?

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#### Solution Preview

Please see attachment! See calculations with red color!

The following observations are recorded:

Diet A Diet B Total

Cancer 30(a) 60(b) 90 (a+b)

No Cancer 353 (c) 357(d) 710 (c+d)

Total 383 (a+c) 417(b+d) 800(a+b+c+d)

Df= (r-1)(k-1)= (2-1)(2-1)= 1

A. Assume these are prospective data.

Please formulate an appropriate null hypothesis addressing whether diet affected the development of cancer, evaluate that null hypothesis, draw conclusions, and apply statistical inference, if appropriate (show all calculations explicitly). (5 points)

Ho: cancer is independent of diet; RRcancer = 1.0; = 0.05

H1: the development of cancer will be affected by differences between diets A and B

Probability of cancer, diet A: a/(a + c) = 30/383 = 0.0783

Probability of cancer, diet B: b/(b + d) = 60/417 = 0.1439

Relative Risk ratiocancer = RRcancer = [a/(a + c)]/[b/(b + d)] = 0.0783/ 0.1439= 0.5441

Ea = [(a + ...

#### Solution Summary

The expert examines the calculations for the chi square tests.