A parenting magazine reports that the average amount of wireless data used by teenagers each month is 5Gb. For her science fair project, Ella sets out to prove the magazine wrong. She claims that the mean among teenagers in her area is less than reported. Ella collects information from a simple random sample of 25 teenagers at her high school, and calculates a mean of 4.7Gb per month with a standard deviation of 0.9Gb per month. Assume that the population distribution is approximately normal. Test Ella’s claim at the 0.01 level of significance.

Step 2 of 3:

Compute the value of the test statistic. Round your answer to three decimal places.