Question 1 Researchers want to find a way to increase the growth rate of corn so it can be harvested more often. To test the effectiveness of a new type of spray fertilizer, plants grown from 200 corn seeds were divided equally into two groups: a treatment group and a control group. The treatment group was frequently sprayed with the new type of fertilizer. The growth in centimeters of each corn plant was noted before and after the treatment.

The results showed that the mean change in the growth rate by the treatment group is 8 points more than that of the control group. To test whether the results could be explained by random chance, researchers created a table that summarizes the results of 1,000 re-randomizations of the data with differences of means rounded to the nearest 2 points.

Consider the significance level to be set at 5%, so results less than 5% can be considered statistically significant.

Treatment Group Mean − Control Group Mean Frequency
Part A
Question
Determine the probability of the treatment group’s mean being greater than the control group’s mean by 8 points or more. Then complete the statements.

The significance level is set at 5%, and the probability of the result is
3.6
%, which is
greater than
the significance level. The result is
statistically significant