SOLUTION: In a study of retention rates of those using the Platinum Program at Jenny Craig in May 2001-May 2002, it was found that about 25% of those who began the program dropped out in the

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Question 1176921: In a study of retention rates of those using the Platinum Program at Jenny Craig in May 2001-May 2002, it was found that about 25% of those who began the program dropped out in the first four weeks. If we have a random sample of 226 people at the beginning of the program, what is the probability that at least 178 people in the sample will still be in the Platinum Program after the first four weeks?
Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
normal approximation
mean is np=226*0.75=169.5
variance is np(1-p)=169.5*0.25=42.475
sd is sqrt(V)=6.51
want z > (177.5-169.5)/6.51, using the continuity correction factor
z> 8/6.51, or 1.23
probability is 0.1093
exact value is 1-0.8918=0.1082