statistics
posted by miriam on .
of all 3to 5year old children, 56% are enrolled in school. If a sample of 500 such children is randomly selected, find the probability that at least 250 will be enrolled in school.

Find mean and standard deviation. Use zscores to find z, then a ztable to find your probability based on the zscore. This is a normal approximation to the binomial distribution.
I'll get you started:
mean = np = (500)(.56) = ?
standard deviation = √npq = √(500)(.56)(.44) = ?
Note: q = 1  p
Finish the calculations.
To find zscore:
z = (x  mean)/sd
Note: x = 250
Once you have the zscore, look in a ztable using the score to find your probability. Remember that the question is asking "at least 250" when looking at the table. 
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