SOLUTION: A research firm needs to estimate within 3% the proportion of junior executives leaving large manufacturing companies within three years. A 0.95 degree of confidence is to be used.

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Question 924483: A research firm needs to estimate within 3% the proportion of junior executives leaving large manufacturing companies within three years. A 0.95 degree of confidence is to be used. Several years ago, a study revealed that 21% of junior executives left their company within three years. To update this study, how many junior executives should be surveyed?
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
ME = z%2Asqrt%28%28p%281-p%29%29%2Fn%29
...
ME = .03
.95 degree of confidence
n = p(1-p)(z/ME)^2
n = (.21)(.79)(1.96/.05)^2 = 255 (rounded to next Integer)