Question

part #1 - evaluating student work of practice frq #1
researchers conducted a study to investigate the effect of exercise on the concentration of prolactin in the blood plasma of humans. they measured the concentration of prolactin in the blood of eight male subjects before (t = 0 hours) and after each had (t = 1 hour) of vigorous exercise. as a control, they measured the concentration of prolactin in the blood of a separate group of eight male subjects of daily use week, but without having them exercise. the results are shown in figure 1.

a. justify the use of the without - exercise treatment as the control in the study design.

b. using evidence from the specific testaments, determine whether prolactin release changes after exercise. justify your answer.

ann
a. the without - exercise treatment serves as the control group to see what normal levels of prolactin are, without exercise, at that exact time. it removes time as a possible variable.
b. prolactin release does not change after exercise because the error bars from t = 0 hour and t = 1 hour on the with - exercise bars overlap.

bob
a. the without - exercise treatment is a control because if the scientist were to just test with exercising they would not be able to tell what increase or decrease in release of prolactin there was. the no - exercise shows the release of prolactin on a normal basis so it can be compared to the release of prolactin with exercise, so a conclusion can be drawn on what effect exercise had on prolactin release.
b. prolactin release increase with exercise because after an hour with exercise treatment blood plasma prolactin increased from 6.1 nmol/l to 7.2 nmol/l. while without exercise after 1 hour prolactin levels went from about 6.4 nmol/l to 6 nmol/l.

carl
a. the without - exercise allows the researchers to have data to compare the with - exercise group with.
b. prolactin release does not change after exercise because the bar after 1 hours falls within the standard error bars of the t = 0 hour bar in the with - exercise group.

prolactin release frq

	possible points	ann	bob	carl	total (max)
(b) determination (1 pt)	1	- determines exercise does not affect prolactin release - justification (1 pt) - the ±2sem error bars for the t = 0 and t = 1 hour with - exercise points overlap or - the ±2sem error bars for the t = 1 hour with - exercise and t = 1 hour without - exercise overlap
total points	3

no partial credit (half points) can be awarded. you either get the full possible points per bullet or you do not.

Explanation:

For part (a), the without - exercise treatment is a control as it gives a baseline for normal prolactin release to compare with the exercise group. For part (b), different conclusions are drawn based on whether the error bars overlap. Ann and Bob think prolactin release changes with exercise while Carl thinks it doesn't as the error bars overlap.

Answer:

a. The without - exercise treatment is a control to show normal prolactin release for comparison.
b. Ann and Bob conclude prolactin release increases with exercise based on level changes. Carl concludes it doesn't change as error bars overlap.