An occupational health practitioner wishes to find out whether there is a statistically significant association between level of exposure to coal dust (low, moderate, high) and stage of lung disease (low, moderate, high) based on data gathered from a random sample of n = 400 mine workers at Kimberley: The expected values are in brackets. The calculated value of Y 2 , the chi-square statistic used to test the null hypothesis of independence, is equal to: Select one: a. 126.62 b. 50.633 c. 20.68 d. 53.28 .