Question

A cell phone company claims that the average time a person spends on their phone is 12.8 hours a week. A sample of unknown size of phone users was selected, and the mean time they spent on their phones was 12.2 hours in a week, with a standard deviation of 2.3 hours. Using a 90% confidence level, how many people would the company have to sample in order for their hypothesis to be true

Answer 1

30

Explanation:

The sample size should be 30 for the given confidence interval of 90%.

Sample size is calculated as follows:

Sample size = Z score ^2 * standard deviation * [ 1 - Standard deviation] / margin of error^2

For the given 90% confidence level, the sample size calculated as;

Sample size = 1.645^2 * 2.3 [1 - 2.3] / 0.01^2

sample size = 30.