The duration of human pregnancies from conception to birth varies according to a distribution approximately Normal with mean 266 days and standard deviation 16 days. Choose two pregnancies independently and at random.What is the expected difference in the lengths of the two pregnancies?What is the standard deviation of the difference in the lengths of the two pregnancies?
Q. The duration of human pregnancies from conception to birth varies according to a distribution approximately Normal with mean 266 days and standard deviation 16 days. Choose two pregnancies independently and at random.What is the expected difference in the lengths of the two pregnancies?What is the standard deviation of the difference in the lengths of the two pregnancies?
Calculate Expected Difference: Calculate the expected difference in the lengths of the two pregnancies.Since we are dealing with a normal distribution with a mean of 266 days, the expected value (mean) of the difference between any two pregnancies chosen at random would be 0. This is because the expected value of the difference between two identical distributions is 0.Calculation: 266−266=0
Calculate Standard Deviation: Calculate the standard deviation of the difference in the lengths of the two pregnancies.The standard deviation of the difference between two independent variables is the square root of the sum of the variances of these variables. Since both pregnancies are independent and have the same standard deviation, the variance for each is the square of the standard deviation 16 days).Calculation: Variance for each pregnancy = 162=256Sum of variances = 256+256=512Standard deviation of the difference = 512=2×256=2×16
Finalize Standard Deviation: Finalize the standard deviation of the difference.Calculation: Standard deviation of the difference = 2 * 16≈1.414 * 16≈22.624 days
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