A study published in the New England Journal of Medicine compared two medicines to treat head lice: an oral medication called ivermectin and a topical lotion containing malathion. Researchers studied 812 people in 376 households in seven areas around the world. Of the 185 households randomly assigned to ivermectin, 171 were free from head lice after 2 weeks, compared with only 151 of the 191 households randomly assigned to malathion.

a. Calculate the difference (Ivermectin – Malathion) in the proportion of households that were free from head lice in the two groups. One hundred trials of a simulation were performed to see what differences in proportions would occur due only to chance variation in the random assignment, assuming that the type of medication doesn’t matter. The results are shown in the dotplot.

b. There is one dot at 0.09. Explain what this dot means in this context.

c. Use the results of the simulation to determine if the difference in proportions from part (a) is statistically significant. Explain your reasoning.

Transcribed Image Text:

-0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 Simulated difference (Ivermectin - Malathion) in proportion who were free from head lice