A researcher wants to assess the effect of stepping rate on heart rate in a stepaerobics workout. She also wants to examine whether the effect of stepping rate on heart rate depends on the volunteer's gender. She takes 30 adult volunteers, 15 women, and 15 men, and randomly divided them into three subgroups. Each subgroup performs a standard stepaerobics workout, with subgroup 1 at a low rate of stepping, subgroup 2 at a medium rate of stepping, and subgroup 3 at a rapid rate of stepping. The researcher measures the mean heart rate at the end of the workout in beats per minute. The ANOVA results of the general linear model analysis are shown in the table.

Source of variationSum of squares dfMean square F P

STEPRATE 2553.2 2 1276.6 5.32 0.012

GENDER 70.7 1 70.7 0.29 0.595

STEPRATE*GENDER 231.7 2 115.9 0.48 0.623

Residual 5762 24 240.1

Total 8617.6 29

Using the table, determine which main effect is statistically significant:

(a) The main effect of STEPRATE*GENDER is statistically significant.

(b) The main effect of STEPRATE is statistically significant.

(c) The main effect of GENDER is statistically significant.

(d) The main effects of STEPRATE and of GENDER are statistically significant.

Based on these results, does the effect of stepping rate on heart rate depend on gender?

(a) No, the interaction between STEPRATE and GENDER is not statistically significant.

(b) Yes, the interaction between STEPRATE and GENDER is statistically significant.

(c) Yes, the interaction between STEPRATE and GENDER is not statistically significant.

(d) No, the interaction between STEPRATE and GENDER is statistically significant.