1a) Calcium is important to the bone development of young girls. To study how th

Question

1a) Calcium is important to the bone development of young girls. To study how the bodies of young girls process calcium, investigators used the setting of a summer camp. Calcium was given in punch at either a high or a low level. The camp diet was otherwise the same for all girls. Suppose that there are 40 campers. Outline a completely randomized design for this experiment.

True or False?

1b) Describe a matched pairs design in which each girl receives both levels of calcium (with a washout period between).

A) Randomly select 20 pairs of girls. In each pair, one subject receives high-calcium punch and the other receives low-calcium punch. Compute the difference in the response variable for each pair.

B) Randomly select 20 girls to receive high-calcium punch first (and low-calcium punch later), while the others get low-calcium punch first (followed by high-calcium punch). For each subject, compute the difference in the response variable for each level.

C) None of the designs is adequate.

D) Randomly select 20 girls to receive high-calcium punch, the others will receive low-calcium punch. Compute

the difference in mean response for the two groups.

1c) True or False?
The matched-pairs design has the advantage of comparing each subject with himself (or with a similar subject) rather than comparing groups of randomly assigned subjects, where lurking parameters are more likely to influence the result.

Explanation / Answer

1)a)

The completely randomized design is design in which participants are randomly assigned to treatments. The given outline indicates that the allocation of girls to the two groups were random. And the treatment for the two groups are different. So, this is a completely randomized design.

So its TRUE statement.

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b)

A matched pair design can be done in two ways -

1) each person receives both treatments or

2) match two people as best as possible (same diets, weight, body mass index, etc), then randomize in the pairs who gets what. In case 1, half receive high level first, and half low level first, then switch with a “washout period” in between.)

So, none of the designs correctly explains the matched pair experiment.

Hence, option (C) is correct.

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C)

The advantage of matched pair design is that it deals with person-to-person variation (AKA between groups variation)

So, the mentioned statement is TRUE.

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