A survey in the U.K. interviewed shoppers encountered in grocery stores about whether they had ever received injuries as a result of food or drink packaging, such as cuts sustained while cleaning up broken glass containers (Winder et al. 2002). Of the 200 who agreed to participate, 109 had received injuries “over the last few years” (27% of those injuries were significant enough to be treated by a doctor or emergency room).

a. What is the best estimate, and 95% confidence interval, for the proportion of shoppers in the population who have injured themselves with their food or drinks?

b. Do you think this was a random sample of all U.K. consumers? What factors might have rendered it a non-random sample?

c. If the sample were biased in some way, how would that affect the interpretation of the confidence interval you calculated in part (a)?