Question

The Centers for Disease Control and Prevention (CDC) report that gastroenteritis, or stomach flu, is the most frequently reported type of recreational water illness. Gastroenteritis is a viral or bacterial infection that spreads through contaminated food and water. Suppose that inspectors wish to determine if the proportion of public swimming pools nationwide that fail to meet disinfectant standards is different from 10.7%, which was the proportion of pools that failed the last time a comprehensive study was done, 2008.

A simple random sample of 30 public swimming pools was obtained nationwide. Tests conducted on these pools revealed that 26 of the 30 pools had the required pool disinfectant levels.

Does this sample meet the requirements for conducting a one-sample z ‑test for a proportion?

a. No, the requirements are not met because the population standard deviation is not known.
b. No, the requirements are not met because the sample has fewer than 10 failures, which violates the condition for approximating a normal distribution.
c. No, the requirements are not met because the sample is not random, even though the number of successes and the number of failures are both at least 10, ensuring that the distribution is approximately normal.
d. Yes, the requirements are met because the sample size is more than 30, ensuring that the distribution is approximately normal.
e. Yes, the requirements are met because the number of successes and the number of failures of this random sample are both at least 10, ensuring that the distribution is approximately normal.

Answer 1

b. No, the requirements are not met because the sample has fewer than 10 failures, which violates the condition for approximating a normal distribution.

Explanation:

from the question, the number of successes is equal to 30

and it is more than the number of failures

for us to conduct this test such as the z test the data we are using should be a random sample from the population that we are interested in. the population should be at least as big as the sample by 10 times. first of all We need to check if the mean of the sample is normally distributed.

if 26 are successes out of a sample of 30, then failures would be 4. therefore option b is correct.