Question

Requirements A quality control analyst has collected a random sample of 12 smartphone batteries and she plans to test their voltage level and construct a 95% confidence interval estimate of the mean voltage level for the population of batteries. What requirements must be satisfied in order to construct the confidence interval using the method with the t distribution?

Short answer

The following two requirements should be satisfied to construct a confidence interval estimate using the student’s t distribution:

• Randomly selected sample
• Unknown sigma value
• The population should be normally distributed.

Step-by-step solution

Given information

A sample of smartphone batteries of size equal to 12 is selected.

The mean voltage of the batteries is to be estimated using a 95% confidence interval.

Requirements

The following requirements need to be satisfied to construct a confidence interval estimate using the student’s t distribution:

• The sample should be a simple random sample.

• The standard deviation of the population must be unknown; that is, \({\bf{\sigma }}\) is not defined.

• The population from which the sample data is chosen should be normally distributed.