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Approximately 20% of newborns are born more than 1 week before their due date. A random sample of 20 newborns is selected.
The standard deviation of the sampling distribution for the proportion of your sample that is born more than 7 days before their due date is
(A) 0.20 
(B) 3.2 
(C) 0.089
(D) 0.008

Approximately 20%20\% of newborns are born more than 11 week before their due date. A random sample of 2020 newborns is selected.\newlineThe standard deviation of the sampling distribution for the proportion of your sample that is born more than 77 days before their due date is\newline(A) 0.200.20 \newline(B) 3.23.2 \newline(C) 0.0890.089\newline(D) 0.0080.008

Full solution

Q. Approximately 20%20\% of newborns are born more than 11 week before their due date. A random sample of 2020 newborns is selected.\newlineThe standard deviation of the sampling distribution for the proportion of your sample that is born more than 77 days before their due date is\newline(A) 0.200.20 \newline(B) 3.23.2 \newline(C) 0.0890.089\newline(D) 0.0080.008
  1. Identify Proportion: First, we need to identify the proportion of newborns born more than 11 week early, which is 20%20\% or 0.200.20.
  2. Calculate Standard Deviation: Next, we calculate the standard deviation of the sampling distribution for the proportion using the formula for the standard deviation of a sample proportion: \newlineStandard deviation = (p×(1p))/n\sqrt{\left(p \times (1 - p)\right) / n}\newlinewhere pp is the proportion and nn is the sample size.
  3. Plug in Values: Plug in the values: p=0.20p = 0.20 and n=20n = 20.\newlineStandard deviation = (0.20×(10.20))/20\sqrt{\left(0.20 \times (1 - 0.20)\right) / 20}
  4. Do the Calculation: Do the calculation:\newlineStandard deviation = (0.20×0.80)/20\sqrt{\left(0.20 \times 0.80\right) / 20}\newlineStandard deviation = 0.16/20\sqrt{0.16 / 20}\newlineStandard deviation = 0.008\sqrt{0.008}
  5. Calculate Square Root: Finally, calculate the square root of 0.0080.008. Standard deviation = 0.0080.089\sqrt{0.008} \approx 0.089 (rounded to three decimal places).

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