Question

Dr. Grey wanted to see if doctors prescribed different treatments for OCD for male patients compared to females. Please use the following frequency tables for the data collected by Dr. Grey.

Contingency table of Observed and Expected Frequencies of the different treatments (Drug vs. Cognitive Therapy) prescribed for patients with OCD.
Therapy Totals		Drug		Cognitive Therapy		Total
Gender of Patient		Observed	Expected	Observed	Expected
	Man	20		10		30
	Woman	15		15		30
	Total	35		25		60

What is the critical value?

A) 3.84

B) 5.99

C) 4.00

D) 2.71

Answer 1

This test is independent chi square test.

Here we do not have level of significance, so default it is 0.05.

Therapy Totals		Drug	Cognitive Therapy
Gender of patient	Man	20	10
	Woman	15	15

We have 3 rows and 2 columns.

So df = ( r-1)(c-1) = ( 2-1)(2-1) = 1*1 = 1

Hence the critical value is,

-----------( Using excel formula " =chisq.inv.rt(0.05,1)" )

Hence the correct option is A) 3.84.