You have been asked to estimate the proportion of households in Chicago that have two or more vehicles. a) How many households would you need to sample to be within 1.5 percent of the proportion of...

You have been asked to estimate the proportion of households in Chicago that have two or more vehicles.

a) How many households would you need to sample to be within 1.5 percent of the proportion of all households in Chicago that have two or more vehicles at a 95% level of confidence.

b) You conduct a small preliminary sample, and you obtain a sample proportion of 20% that have two or more cars. Using this new information, what sample size should you gather in order to be within 1.5 percent of the proportion of all households in Chicago that have two or more vehicles at a 95% level of confidence.