Question

1. 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 number 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 gives better weed control than the standard weed killer.
b. for both chemicals, fewer weeds 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. the high concentration of the standard weed killer was more effective than the low concentration of the new chemical.

Explanation:

Step1: Analyze option a

Looking at the box - plots, for both high and low concentrations, the box - plots of the new chemical (N) are to the left of the standard weed killer (S) in terms of the number of weeds. A lower number of weeds means better weed control. So, at both high and low concentrations, the new chemical gives better weed control than the standard weed killer. This statement is correct.

Step2: Analyze option b

For the standard weed killer (S), the high - concentration box - plot (S - high conc) is to the left of the low - concentration box - plot (S - low conc). For the new chemical (N), the high - concentration box - plot (N - high conc) is to the left of the low - concentration box - plot (N - low conc). So, for both chemicals, fewer weeds grew at higher concentrations than at lower concentrations. This statement is correct.

Step3: Analyze option c

The inter - quartile range (IQR, the length of the box in a box - plot) for the standard weed killer (S) (both high and low concentrations) is smaller than that for the new chemical (N) (both high and low concentrations). A smaller IQR means less variability. So, the results for the standard weed killer are less variable than those for the new chemical. This statement is correct.

Step4: Analyze option d

The high - concentration of the standard weed killer (S - high conc) has a higher median (the line inside the box) than the low - concentration of the new chemical (N - low conc). So, the high concentration of the standard weed killer was not more effective (more weeds grew) than the low concentration of the new chemical. This statement is incorrect.

Answer:

d. The high concentration of the standard weed killer was more effective than the low concentration of the new chemical.