A researcher studying ADHD among teenagers obtains a simple random sample of 100 teenagers aged 13-17 and asks them whether or not they have ever been prescribed medication for ADHD. To say that the distribution of pn, the sample proportion of teenagers who respond no, is approximately normal, how many more teenagers aged 13-17 does the researcher need to sample if
(a) 90% of all teenagers aged 13-17 have never been prescribed medication for ADHD?
(b) 95% of all teenagers aged 13-17 have never been prescribed medication for ADHD?