Answer:
The p-value of the test is of 0.0287 < 0.05(standard significance level), which means that it can be concluded that less than half of HIV-positive smokers have used a nicotine patch.
Step-by-step explanation:
Test if less than half of HIV-positive smokers have used a nicotine patch:
At the null hypothesis, we test if the proportion is of at least half, that is:
![H_0: p \geq 0.5](https://tex.z-dn.net/?f=H_0%3A%20p%20%5Cgeq%200.5)
At the alternative hypothesis, we test if the proportion is below 0.5, that is:
![H_1: p < 0.5](https://tex.z-dn.net/?f=H_1%3A%20p%20%3C%200.5)
The test statistic is:
![z = \frac{X - \mu}{\frac{\sigma}{\sqrt{n}}}](https://tex.z-dn.net/?f=z%20%3D%20%5Cfrac%7BX%20-%20%5Cmu%7D%7B%5Cfrac%7B%5Csigma%7D%7B%5Csqrt%7Bn%7D%7D%7D)
In which X is the sample mean,
is the value tested at the null hypothesis,
is the standard deviation and n is the size of the sample.
0.5 is tested at the null hypothesis:
This means that ![\mu = 0.5, \sigma = \sqrt{0.5*(1-0.5)} = 0.5](https://tex.z-dn.net/?f=%5Cmu%20%3D%200.5%2C%20%5Csigma%20%3D%20%5Csqrt%7B0.5%2A%281-0.5%29%7D%20%3D%200.5)
In a survey of 444 HIV-positive smokers, 202 reported that they had used a nicotine patch to try to quit smoking.
This means that ![n = 444, X = \frac{202}{444} = 0.455](https://tex.z-dn.net/?f=n%20%3D%20444%2C%20X%20%3D%20%5Cfrac%7B202%7D%7B444%7D%20%3D%200.455)
Value of the test statistic:
![z = \frac{X - \mu}{\frac{\sigma}{\sqrt{n}}}](https://tex.z-dn.net/?f=z%20%3D%20%5Cfrac%7BX%20-%20%5Cmu%7D%7B%5Cfrac%7B%5Csigma%7D%7B%5Csqrt%7Bn%7D%7D%7D)
![z = \frac{0.455 - 0.5}{\frac{0.5}{\sqrt{444}}}](https://tex.z-dn.net/?f=z%20%3D%20%5Cfrac%7B0.455%20-%200.5%7D%7B%5Cfrac%7B0.5%7D%7B%5Csqrt%7B444%7D%7D%7D)
![z = -1.9](https://tex.z-dn.net/?f=z%20%3D%20-1.9)
P-value of the test and decision:
The p-value of the test is the probability of finding a sample proportion below 0.455, which is the p-value of z = -1.9.
Looking at the z-table, z = -1.9 has a p-value of 0.0287.
The p-value is of 0.0287 < 0.05(standard significance level), which means that it can be concluded that less than half of HIV-positive smokers have used a nicotine patch.