When a woman learns she is pregnant, her doctor calculates a due date for the ba

Question

When a woman learns she is pregnant, her doctor calculates a due date for the baby. The due date represents the date on which the baby will be born if her pregnancy lasts the mean of all length for all pregnancies. Actual lengths of pregnancy terms turns out to be normally distributed about this due date (the mean) with a standard deviation of 15 days.

a) About what percent of births occur within 15 days of the due date?

b) About what percent of births occur within 1 month of the due date (assume 30 days or 2 standard deviations-hint)?

Explanation / Answer

a) 15 days lie within 1 standrad deviation of normal distribution

so percent of data that lies with 1 standard deviation is 68% according to normal distribution curve

hence, 68 percent of births occur within 15 days of the due date

b) about 95% data lies withing 2 standard deviation

therefore , 95 percent of births occur within 1 month of the due date

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