This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Biostatistics, Subject name: Social & Preventive Medicine
Test of association between two variables is done by- 
Select and explain. 
A. X2, B. Correlation, C. Regression, D. None
B: Correlation
Answer: B: Correlation 
Explanation: Ref:Parks 23rd edition pg 852 In order to find out whether there is significant association or not between the two variables , coefficient or Corelation is calculated . r lies between -1 and +1 r near -1 : indicates strong negative correlation . r = 0 : indicates no association r near +1: indicates strong positive correlation. Note: correlation does not necessarily prove causation . Chi-square test offers an alternate method of testing the significance of difference between two propoions.Advantage: it can also be used when more than 2groups are to be compared.