A nutritionist claims that a new diet program helps participants lose an average of 8 kilograms in two months. To test this claim, a researcher selects a random sample of 25 participants who followed the program. The sample shows an average weight loss of 7.2 kilograms with a sample standard deviation of 1.5 kilograms. At the 5% significance level, can the researcher conclude that the true mean weight loss is less than 8 kilograms? Find the Test Statistic.