The proportion of deaths due to lung cancer in males ages 15-64 in England and Wales during the period 1970-1972 was 12%. Suppose that of 20 deaths that occur among male workers in this age group who have worked for at least 1 year in a chemical plant, 5 are due to lung cancer. We wish to determine whether there is a difference between the proportion of deaths from lung cancer in this plant and the proportion in the general population.
Is a one-sided or two-sided test appropriate here?" Explain
I think 2 sided because we have no prior information that the proportion of lung cancer deaths is higher or lower than the general population.
You are correct. In this scenario, a two-sided test is appropriate because there is no prior information or hypothesis suggesting that the proportion of lung cancer deaths in the chemical plant workers is specifically higher or lower than the general population.
A one-sided test would be appropriate if there was a strong prior belief or hypothesis that the proportion of lung cancer deaths in the plant workers should be either higher or lower than the general population. However, since there is no such prior belief, a two-sided test is preferred as it keeps both possibilities open for investigation.