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Course: AP®︎/College Statistics > Unit 9

Lesson 6: Sampling distributions for sample means
Math
AP®︎/College Statistics
Sampling distributions
Sampling distributions for sample means
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Mean and standard deviation of sample means

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Problem

A light bulb manufacturer claims that a certain type of bulb they make has a mean lifetime of 1000 hours and a standard deviation of 20 hours. Each package sold contains 4 of these bulbs. Suppose that each package represents an
of bulbs, and we calculate the sample mean lifetime x¯ of the bulbs in each package.
Calculate the mean and standard deviation of the sampling distribution of x¯.
μx¯=
  • Your answer should be
  • an integer, like 6
  • a simplified proper fraction, like 3/5
  • a simplified improper fraction, like 7/4
  • a mixed number, like 1 3/4
  • an exact decimal, like 0.75
  • a multiple of pi, like 12 pi or 2/3 pi
hours
σx¯=
  • Your answer should be
  • an integer, like 6
  • a simplified proper fraction, like 3/5
  • a simplified improper fraction, like 7/4
  • a mixed number, like 1 3/4
  • an exact decimal, like 0.75
  • a multiple of pi, like 12 pi or 2/3 pi
hours