Question

Treatment with statins can reduce the risk of a major cardiovascular event in people with specified risk factors. During about 2 years of follow-up in the JUPITER trial, 142 of 8901 subjects treated with a statin had a major cardiovascular event.

1)First, estimate the 2-year risk, and give a 95% confidence interval for this estimate. Assuming that risk remains constant over time, give an estimate of the 10-year risk of a major cardiovascular event on statin therapy.

2)Suppose the expected 2-year risk of a major cardiovascular event in similar but untreated people is 0.028. Test whether the 2-year risk in those treated with a statin is significantly different from this expected risk at the 5% level. Make sure to state your null and alternative hypotheses and specify your conclusion.

Answer 1

1. The 95% confidence interval for this estimate is between 0.013 and 0.019.

2. The hypothesis being tested is:

H0: p = 0.028

Ha: p ≠ 0.028

The test statistic is -6.89.

The p-value is 0.0000.

Since the p-value (0.0000) is less than the significance level (0.05), we can reject the null hypothesis.

Therefore, we can conclude that the 2-year risk in those treated with a statin is significantly different from this expected risk.

Observed	Hypothesized
0.016	0.028	p (as decimal)
142/8901	249/8901	p (as fraction)
142.	249.228	X
8901	8901	n
	0.002	std. error
	-6.89	z
	5.61E-12	p-value (two-tailed)
	0.013	confidence interval 95.% lower
	0.019	confidence interval 95.% upper
	0.003	margin of error

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