posted by Juliet on .
Suppose 60% of adults have a college degree. If I take a random sample of 80 adults, what is the probability at least 50% of them have a college degree?
Use the normal approximation to the binomial distribution.
mean = np = 80 * .6 = ?
standard deviation = √npq = √(80 * .6 * .4) = ?
Calculate. (Note: q = 1 - p)
Next use z-scores:
z = (x - mean)/sd
x = 80 * .5 = ?
Once you have the z-score, find the probability using the z-table.
I hope this will help get you started.