116 Exposure to low-frequency sound. Infrasound refers to sound frequencies below the audibility range of the human ear. A study of the physiological effects of infrasound was published in the Journal of Low Frequency Noise , Vibration and Active Control (Mar. 2004). In the experiment, one group of five university students (Group A) was exposed to infrasound at 4 hertz and 120 decibels for 1 hour, and a second group of five students (Group B) was exposed to infrasound at 2 hertz and 110 decibels, also for 1 hour. The heart rate (beats/minute) of each student was measured both before and after exposure.
The experimental data are provided in the accompanying table and saved in the INFRASOUND file. To determine the impact of infrasound, the researchers compared the mean heart rate before exposure to the mean heart rate after exposure.

a. Analyze the data on Group A students with an ANOVA for a randomized block design. Conduct the ANOVA test of interest with a = .05 .

b. Repeat part a for Group B students.

c. Now analyze the data via a paired difference t -test.
Show that, for both groups of students, the results are equivalent to the randomized block ANOVA.

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Group A Before After Group B Before After Students Exposure Exposure Students Exposure Exposure A1 70 A2 69 A3 76 A4 77 A5 64 P8487 70 B1 73 80 B2 68 84 B3 61 86 B4 72 76 B5 61 28876 79 60 69 77 66 Based on Qibai, C. Y. H., and Shi, H. "An investigation on the physiological and psychological effects of infrasound on persons." Journal of Low Frequency Noise, Vibration and Active Control, Vol. 23, No. 1, March 2004 (Tables I-IV).