Answer:
Take u1 = average number of mosquitoes attracted after drinking beer
u2 = average number of mosquitoes attracted after drinking water
a) The null and alternative hypotheses:
H0 : u1 = u2
H1 : u1 > u2
b) i) The average number of mosquitoes per volunteer before drinking (beer group) :
Sample mean for mosquitoes attracted before consumption for beer group is 17.36
The average number of mosquitoes per volunteer before drinking (water group) :
Sample mean for mosquitoes attracted before consumption for water group is 18.72
The two means are different.
The difference in the two means are as a result of random choice.
c) i) The average number of mosquitoes per volunteer after drinking (beer group) :
Sample mean for mosquitoes attracted after consumption for beer group is 23.60
ii) The average number of mosquitoes per volunteer after drinking (water group) :
Sample mean for mosquitoes attracted after consumption for water group is 19.17
The two sample means are different.
This difference here is likely not to be as a result of random choice, because the mean difference here is greater than the mean difference before consumption.
d) A statistically significant difference provides evidence that beer consumption increases mosquito attraction, as the average number of mosquitoes attracted when drinking beer is higher than the mean number of mosquitoes attracted when drinking water.