Suppose that an advertisement claims the average weight loss for someone on a new fad diet is 15 pounds, with a standard deviation of 4 pounds. A sample of 18 adults enrolled in a new diet program...

Suppose that an advertisement claims the average weight loss for someone on a new fad diet is 15 pounds, with a standard deviation of 4 pounds. A sample of 18 adults enrolled in a new diet program have a mean weight loss of 15.83 pounds. Test that average weight loss is different than the advertised 15 pounds, at a significance level of 0.10.

Wha is the test statistic?