A nutritionist is interested in whether excessive sugar intake causes hyperactiv

Question

A nutritionist is interested in whether excessive sugar intake causes hyperactivity in children. Two different study designs are contemplated to examine this issue.

Design I – One hundred children with their parents’ permission are to be subjects in the study. The nutritionist will randomly divide the children into two groups of fifty. Both groups of children will eat similar diets for a week, including a bowl of cereal, a sandwich, a main course, four glasses of a special milkshake, and two candy bars per day. However, in preparing the food in one of the groups’ diets, all of the sugar is to be replaced with an artificial sweetener (so the children cannot tell the difference between the two diets). A psychologist who does not know which diet the children were on will then watch them at play and classify each child as showing signs of hyperactivity or showing no signs of hyperactivity.

Design II – One hundred children will be watched while they play by a psychologist who will classify each child as showing signs of hyperactivity or showing no signs of hyperactivity. This data will then be compared with the results of a diet questionnaire filled out by the children’s parents that gives information about the children’s sugar intake over the previous week.

a. Label the response and explanatory variables below for each design:

·       Design I
Response variables:

Explanatory variables:

·       Design II
Response variables:

Explanatory variables:

b. Which design is an observational study and which is an experiment?

c. Which of these study designs is likely to be easier to carry out?

d. Which design would give more convincing evidence about the relationship between sugar intake and hyperactivity? Explain.

Explanation / Answer

a) Design I

RV: response of Hyperactivity

EV: Sugar Intake

Design II:

RV: response of Hyperactivity

EV: Sugar Intake

b) Design I is experimental and Design II is Observational study

c) Design II

d) Design I, because all other factors which can influence the results are in control of nutritionist

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