Aresearcher wishes to estimate, with 90% 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 22% of motor vehicle fatalities that were caused by alcohol-impaired driving. (c) compare the results from parts (a) and (b).