Question

a student designed an experiment to investigate a claim that athletes would have lower heart rates than non - athletes during exercise. after the students classified themselves as an athlete or a non - athlete, their resting pulses were determined. then all the students performed the same exercise for four minutes and their heart rates were determined by recording the pulse rate in beats per minute. the students continued to measure their pulse rates for an additional four minutes. the average heart rate per minute for each group was determined. the data were recorded, as shown on the table below.

average heart rate response to exercise (beats per minute)

	time (minutes)	athlete students	nonathlete students
exercising period	1	76	78
	2	82	90
	3	95	115
	4	110	130
after exercise	5	100	125
	6	95	120
	7	85	100
	8	68	95

to improve the validity of the conclusion reached in this experiment, the students should repeat the experiment -
a. comparing the heart rates and breathing rates of males and females
b. with the athletes doing different exercises than the non - athletes
c. disregarding any data that dont fit the hypothesis
d. with a larger number of athletes and non - athletes

Explanation:

Increasing the sample size (more athletes and non - athletes) reduces sampling error and makes the results more representative, thus improving the validity of the experiment. Comparing heart and breathing rates of males and females (A) is a different variable and not directly related to the original claim. Having athletes and non - athletes do different exercises (B) violates the control of the experiment. Disregarding data that doesn't fit the hypothesis (C) is unethical and reduces the validity as it biases the results.

Answer:

D. With a larger number of athletes and nonathletes