A researcher wishes to estimate, with

99%

confidence, the population proportion of motor vehicle fatalities that were caused by alcohol-impaired driving. His estimate must be accurate within

3%

of the population proportion.

(a) No preliminary estimate is available. Find the minimum sample size needed.

(b) Find the minimum sample size needed, using a prior study that found that

28%

of motor vehicle fatalities that were caused by alcohol-impaired

driving.

(c) Compare the results from parts (a) and

(b).