Question

At a high school with over 500 students, a counselor wants to estimate the mean number of hours per week that students at the school spend in community service activities. The counselor will survey 20 students in the Environmental Club at the school. The mean number of hours for the 20 students will be used to estimate the population mean. Which of the following conditions for inference have not been met?

1. The data are collected using a random sampling method.
2. The sample size is large enough to assume normality of the distribution of sample means.
3. The sample size is less than 10 percent of the population size.

Answer 1

Complete option:

The sample size is less than 10 percent of the population size. A. II onlyB. III onlyC. II and III onlyD. I, II, and III

Answer:

D.) I, II, and III

Explanation:

The sample are not well randomly selected as the samples were only selected from a single source, the environmental club in the school.

Similarly only 20 samples were chosen, these 20 samples are not enough to assume normality as the minimum number of samples required to assume normality according to the Central limit theorem is 30 samples or more.

10% of the population size is :

Population size = 5000

0.10 * 5000 = 500 samples

Hence, sample size used is less than 10% of population size.