Have you ever noticed that mosquitoes go for some people more than others? A recent study (Khan et al, 2021) used the Asian mosquito Anopheles stephensi, which carries malaria, to investigate whether this might be due to the fact that people have different blood groups. They found that mosquitoes that fed on blood group B laid considerably more eggs than those that fed on the alternative blood groups, A, AB, and O.

The researchers also investigated whether female mosquitoes could detect the more favourable blood groups prior to feeding. They set wind-tunnel trials where the tunnel split into four choices, each of which had a glass jar containing blood from one of the four different blood groups at its end. In each trial, 100 mosquitoes were released. Each mosquito could select from any of the four blood groups by choosing the corresponding arm of the tunnel. After 30 minutes, the number that selected each of the four blood groups was counted.

One of the trials yielded the numbers below. Design a suitable test to decide whether these numbers show evidence of a sys-

tematic bias towards feeding on blood group B. Carry out the test and interpret your findings.