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Question 10 of 13 - Quiz 3

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Attempt 1
The gestation time of humans has an approximate Normal distribution with a mean of 250 days and a standard deviation of 6.0 days. A simple random sample of 
n newborns is to be taken.
What is the minimum sample sized needed so that the sampling distribution of 
bar(x) has a standard deviation of 0.5 day?
144
12
250
15
incorrect

Question 1010 of 1313 - Quiz 33\newline84.6% 84.6 \% \newlineResources\newlineFeedback\newlineResume\newlineAttempt 11\newlineThe gestation time of humans has an approximate Normal distribution with a mean of 250250 days and a standard deviation of 66.00 days. A simple random sample of n n newborns is to be taken.\newlineWhat is the minimum sample sized needed so that the sampling distribution of xˉ \bar{x} has a standard deviation of 00.55 day?\newline144144\newline1212\newline250250\newline1515\newlineincorrect

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Q. Question 1010 of 1313 - Quiz 33\newline84.6% 84.6 \% \newlineResources\newlineFeedback\newlineResume\newlineAttempt 11\newlineThe gestation time of humans has an approximate Normal distribution with a mean of 250250 days and a standard deviation of 66.00 days. A simple random sample of n n newborns is to be taken.\newlineWhat is the minimum sample sized needed so that the sampling distribution of xˉ \bar{x} has a standard deviation of 00.55 day?\newline144144\newline1212\newline250250\newline1515\newlineincorrect
  1. Use formula for standard deviation: Use the formula for the standard deviation of the sampling distribution of the sample mean, which is σ/n\sigma/\sqrt{n}, where σ\sigma is the population standard deviation and nn is the sample size.
  2. Set up equation: We want the standard deviation of the sample mean to be 0.50.5 days. The population standard deviation is 6.06.0 days. So, set up the equation 6.0n=0.5\frac{6.0}{\sqrt{n}} = 0.5.
  3. Square both sides: Square both sides of the equation to solve for nn. (6.0/0.5)2=n(6.0/0.5)^2 = n.
  4. Calculate value of n: Calculate the value of n. (6.0/0.5)2=(12)2=144(6.0/0.5)^2 = (12)^2 = 144.

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