15.For the following question, all you need to decide is which type of test is appropriate.The possible answers are A)z-test for proportions;B)z-test for means;C)t-test for means;D)none of them are appropriate.No explanation is needed.If the sampling distribution isn't normal, then none of them will be appropriate.If the variable is nominal, you would use proportions.[Please note:in some situations, the distinction between a z-test and a t-test is negligible.Please indicate the one that is truly correct.]

A particular diet claims to help people lose weight. A dietician wants to see if this particular diet helps lose weight better than the average diet.He knows that twenty per cent of people on an average diet lose weight. He gets a sample of 120 people.They were weighed before they began dieting. Then they went on the diet for six months. After the six months, the subjects were weighed again. It was recorded whether they lost weight or if they didn't lose weight.