A random sample of 64 bicycle-riding adults in Portland indicated that 24 always wore a helmet while riding. A random sample of 80 bicycle-riding adults in Amsterdam indicated that 18 always rode a helmet while riding.
a. Use the sample information to develop a 95% confidence interval estimate for the difference between the proportions of bicycle-riding adults that wear a helmet in the two cities.
b. Based on the sample results, can you conclude that the population proportion of bicycle-riding adults in Portland who always wear a helmet is greater that the population proportion of bicycle-riding adults in Amsterdam who always wear a helmet? Use a 0.025 level of significance to conduct the test.