Question

An experiment was conducted to investigate the effect of a new weed killer to prevent weed growth in onion crops. Two chemicals were used: the standard weed killer (S) and the new chemical (N). Both chemicals were tested at high and low concentrations on 50 test plots. The percent of weeds that grew in each plot was recorded. Here are some boxplots of the results.

Which of the following is not a correct statement about the results of this experiment

a. At both high and low concentrations, the new chemical results in better weed control than the standard weed killer.

b. For both chemicals, a smaller percentage of weeds typically grew at higher concentrations than at lower concentrations.

c. The results for the standard weed killer are less variable than those for the new chemical.

d. High and low concentrations of either chemical have approximately the same effects on weed growth.

e. Some of the results for the low concentration of weed killer show a smaller percentage of weeds growing than some of the results for the high concentration.

Short answer

The correct option is (d)

d. High and low concentrations of either chemical have approximately the same effects on weed growth.

Step-by-step solution

Step 1. Given information.

a. At both high and low concentrations, the new chemical results in better weed control than the standard weed killer.

b. For both chemicals, a smaller percentage of weeds typically grew at higher concentrations than at lower concentrations.

c. The results for the standard weed killer are less variable than those for the new chemical.

d. High and low concentrations of either chemical have approximately the same effects on weed growth.

e. Some of the results for the low concentration of weed killer show a smaller percentage of weeds growing than some of the results for the high concentration.

Step 2. find the incorrect statement about the experiment's results

(a) Correct, because the S boxplots are more to the right than the N boxplots (at both low and high concentrations), indicating that the new chemical outperforms the standard weed killer.

(b) Correct, because the boxes of the boxplots of higher concentrations tend to lie to the left of the boxes of the boxplots of lower concentrations (for both S and N), implying that the low concentrations typically grew more weeds.

(c) Correct, because the S boxplots are narrower than the N boxplots, indicating that the standard weed killer's results are less variable than the new chemical's results.

(d) Incorrect because the boxes of the boxplots of higher concentrations tend to lie to the left of the boxes of the boxplots of lower concentrations (for both S and N), implying that the low concentrations typically grew more weeds.

(e) Correct, because we see that the lowest percentage of weeds for the low concentration is about 3% and the highest percentage of weeds for the high concentration is about 50%, indicating that the low concentration may have a lower percentage of weeds than the high concentration.

As a result:

The not correct statement.

d. High and low concentrations of either chemical have approximately the same effects on weed growth.