Question

17) According to the American Dietetic Association (ADA), 20% of pregnant women need to increase their energy intake by a factor of 1.5 or more. A random sample of 400 pregnant women is selected.  Describe the Distribution of the Sample Proportion of women needing to up their energy intake by a factor of 1.5 or more—describe the shape, the Mean, and the Standard Deviation.

Answer 1

n = 400 * 0.20 = 80 > 10

n ( 1 - ) = 400 * (1 - 0.20) = 320 > 10

Since n > 10 and n ( 1 - ) > 10

Shape of sampling distribution of sample proportion is approximately normal.

Mean = = 0.20

Standard deviation = sqrt [ ( 1 - ) / n ]

= sqrt [ 0.20 * ( 1- 0.20) / 400 ]

= 0.02