1.Medical researchers studying the effects of a low carb diet versus a normal diet randomly assigned obese patients to one of the two diets. The patients were followed up with after several months and the amount of weight lost (lbs) was recorded. Researchers advised against interpreting these results as a universal endorsement of low-carb diets for the general population wanting to lose weight. Why would the researchers give this advice? (Choose the most appropriate answer).

A.This experiment only used obese subjects.

B.This is an observational study so we cannot establish that the low-carb diet causes weight loss.

C.This experiment did not use blinding.

2.A researcher is interested in studying the effect of iron on human memory so he comes up with the following plan for an experiment. The experiment will involve 100 volunteers where 50 volunteers are randomly selected from all female volunteers and 50 are randomly selected from all male volunteers. Each volunteer will take a memory test 30 minutes after eating spinach. Some volunteers will be randomly assigned to eat iron-free spinach; some will eat regular spinach (with iron); others will eat a mixture of the two which contains only half the amount of iron. For each volunteer, a test score (the number of items recalled correctly) will be recorded. The volunteers will not be told which type of spinach they have been given, but the researcher who evaluates the results will prepare the cans of spinach right on the spot (out of sight of the volunteers).

Part i)What sampling technique is used to obtain the 100 volunteers to participate in the study?

A.One-stage cluster sampling

B.Two-stage cluster sampling

C.Simple random sampling

D.Systematic sampling

E.Stratified random sampling

Part ii)Which of the following features is/are present in this study? CHECK ALL THAT APPLY.

A.Blocking

B.Single blinding

C.Replication

D.Confounding

E.Double blinding

F.None of the above

Part iii)The treatments of this study is/are:

A.iron

B.a can of spinach

C.iron-free spinach and regular spinach with iron

D.no iron, half dose of iron and full dose of iron

3. Refer to the study in the previous question.

The study finds that the group of volunteers who eat regular spinach has a significantly higher average test score than the group who eat iron-free spinach. This implies:

A.The difference in the average test score between the regular spinach group and the iron-free spinach group is so large that it can be explained by chance.

B.The difference in the average test score between the regular spinach group and the iron-free spinach group is so small that it cannot be explained by chance.

C.The difference in the average test score between the regular spinach group and the iron-free spinach group is so large that it cannot be explained by chance.

D.The difference in the average test score between the regular spinach group and the iron-free spinach group is so small that it can be explained by chance.