Out of concern for consumer safety, the Farmer’s Cooperative of Wisconsin and Ralston Purina selected a random sample of 200 dairy cows to assess whether the level of mastitis, a potentially serious bacterial disease found in cows, is related to the type of feed the cows are given. Results from the sample are given below:

Use a chi square test of independence to test a null hypothesis that the level of the disease is independent of feed type. Use a significance level of 1% for your test.

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Feed High Feed 10 20 30 60 Level of Disease Norma Energy Grass Totals 70 80 Moderate High Totals 140 200