91影视

Out of 280 trials, 123 guesses were correct by the touch therapists. It is claimed that that touch therapists randomly guess the answer.

The null hypothesis is written as follows.

The proportion of correct guesses is equal to 0.5.

$H_0:p=0.5$

The alternative hypothesis is written as follows.

The proportion of correct guesses is not equal to 0.5.

$H_1:p鈮�0.5$

The test is two-tailed.

The sample size is n=280.

The sample proportion of correct guesses is computed below.

$$\begin{gathered} \hat{p}=\frac{\text{Number}\text{of}\text{correct}\text{guesses}}{\text{Sample}\text{Size}} \\ =\frac{123}{280} \\ =0.439 \end{gathered}$$

The population proportion of correct guesses is equal to 0.5.

The value of the test statistic is computed below.

$$\begin{gathered} z=\frac{\hat{p}-p}{\sqrt{\frac{pq}{n}}} \\ =\frac{0.439-0.5}{\sqrt{\frac{0.5\left(1-0.5\right)}{280}}} \\ =-2.032 \end{gathered}$$

Thus, z=-2.032.

Referring to the standard normal table, the critical value of z at for a two-tailed test is equal to 2.5758.

Referring to the standard normal table, the p-value for the test statistic value of -2.032 is equal to 0.0422.

As the p-value is greater than 0.01, the null hypothesis is failed to reject.

There is not enough evidence to reject the claim that the touch therapists randomly guess the correct answer.