1. If level of atorvastatin was independent of incidence of headaches, what would be the expected frequency in the headache and 20 mg cell? Would this cause any concern for a test of independence of these factors? Why? 2. Combine the 20 mg and 40 mg results into one column, then perform a chi-squared hypothesis test at the 1% significance level to evaluate the evidence that the incidence of headaches is dependent on the amount of atorvastatin used.
The cholesterol-reducing drug Lipitor consists of atorvastatin calcium. Results (based on data from the company Parke-Davis) summarising the incidence of headaches as an adverse reaction in clinical tests are given below. We are interested in evaluating the evidence that the incidence of headaches is dependent on the amount of atorvastatin used.
| Placebo | Atorvastatin 10 mg | Atorvastatin 20 mg | Atorvastatin 40 mg | Atorvastatin 80 mg | |
| Headache | 19 | 47 | 6 | 2 | 6 |
| No headache | 251 | 816 | 30 | 77 | 88 |
1. If level of atorvastatin was independent of incidence of headaches, what would be the expected frequency in the headache and 20 mg cell? Would this cause any concern for a test of independence of these factors? Why?
2. Combine the 20 mg and 40 mg results into one column, then perform a chi-squared hypothesis test at the 1% significance level to evaluate the evidence that the incidence of headaches is dependent on the amount of atorvastatin used.
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