91影视

The two samples represent independent binomial trials. The arbitrary binomial variables are the figures and of the 1145 and 1142 cases in the angioplasty group and drug-only group, respectively.

The results are epitomized in the table over.

We now calculate the sample proportions and. Of the dropouts in the 1st and 2nd group Independently.

P₁= == 0.1843

P₂= == 0.1769

A large sample 95% confidence interval for the difference (P_{1 - P2}) between the drop rates of the two groups of exercisers is given by

$$\begin{gathered} (P_1-P_2)卤Z_{\frac{a}{2}}脳{蟽}_{(p1-p2)} \\ {P}_1-P_2)卤Z_{\frac{a}{2}}脳\sqrt{\frac{P_1{q}_1}{n_1}}+\frac{P_2{q}_2}{n_2} \end{gathered}$$

Substituting the sample quantities yields

$\left(0.01843-0.1769\right)卤1.96\sqrt{\frac{\left(0.1843\right)\left(0.8157\right)}{1145}+\frac{\left(0.1769\right)\left(0.8231\right)}{1142}}$

(0.1843 鈥� 0.1769) 1.96

- 0.00740.03153

(- 0.02413, - 0.03893)

The interval can be interpreted as follows:

With a confidence coefficient equal to 0.95, we estimate that the difference in the rate of the heart attacks between the cases in the angioplasty group and the cases in the medication-only group falls in the interval from -0.02431 to 0.03893.

In other words, we estimate (with 95% confidence) the rate of heart attack for the medication-only group to be anywhere from 2.413% less than to 3.893% more than the heart attack rate for the angioplasty group.

There is insufficient evidence to indicate that () differs from 0 because the interval includes 0 as a possible value for().