Question

Community acquired methicillin resistant Staphylococcus aureus (CA-MRSA) is a cause of skin infections. A case-control study is conducted to explore the association between having a cat in the household and CA-MRSA. The results of the study are given below. CA-MRSA 146 230 No CA-MRSA 120 504 Cat in household No cat in household

Answer 1

Assuming significance of 0.05 since it's not given in the question.

1) Not Exposed to children case - Relationship between CAT in household and CA-MRSA

Chi-Square statistic for this equals 0.547

Degrees of Freedom = (2-1)*(2-1) = 1

Chi-square critical stat at 1 degrees of freedom = 0.004

0.547>0.004, hence, rejecting null that there is no association between CAT in household and CA-MRSA. Hence, there is association between CAT in household and CA-MRSA.

2) Exposed to children case - Relationship between CAT in household and CA-MRSA

Chi-Square statistic for this equals 0.722

Degrees of Freedom = (2-1)*(2-1) = 1

Chi-square critical stat at 1 degrees of freedom = 0.004

0.722>0.004, hence, rejecting null that there is no association between CAT in household and CA-MRSA. Hence, there is association between CAT in household and CA-MRSA.