A survey is conducted to investigate the relationship between exposure of a mysterious chemical A and specific chronic disease B. The results of the survey are shown as the following contingency table based on exposure status (those with and without chemical A exposure) and disease status (disease B or not).

	Disease B	No diabetes	Total
chemical A exposure	125	75	200
No chemical A exposure	50	150	200
Total	175	225	400

A. Please test whether there is an association between chemical A exposure and disease B.

PLEASE SHOW THE CALCULATIONS FROM THE TABLE

B. Please calculate the odds ratio of having disease B comparing to no disease group under the chemical A exposure and its 95% confidence interval

PLEASE SHOW THE CALCULATIONS FROM THE TABLE