AP Statistics · Topic 5.3

The Central Limit Theorem Practice

Part of Sampling Distributions.(UNC-3.D)

Practice questions

8

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Sample questions

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  1. Sample 1difficulty 2/5

    A statistics teacher is reviewing the conditions under which the sampling distribution of the sample mean is approximately normal.

    Central Limit Theorem Skewed pop. x̄ ~ Normal

    According to the Central Limit Theorem, the sampling distribution of x̄ is approximately normal when which condition holds?

    • A

      The sample size n is sufficiently large (n ≥ 30 is a common rule).

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    • B

      The population is uniform.

    • C

      The population standard deviation is known.

    • D

      The sample mean equals the population mean.

    Why

    The CLT states that for sufficiently large n, the sampling distribution of x̄ is approximately normal regardless of the population shape.

  2. Sample 2difficulty 2/5

    CLT rule of thumb n ≥ 30

    A common rule of thumb says the CLT applies when which condition holds for a moderately skewed population?

    • A

      n ≥ 30.

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    • B

      n ≥ 100.

    • C

      Only when σ is known.

    • D

      n ≥ 5.

    Why

    For moderately skewed populations, n ≥ 30 typically suffices.

  3. Sample 3difficulty 3/5

    A population is strongly right-skewed. A sample of n = 5 is taken.

    Strong Skew, n = 5

    What can you say about the sampling distribution of x̄?

    • A

      It is approximately normal by the CLT.

    • B

      It is uniform.

    • C

      It is also right-skewed because n is too small for the CLT.

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    • D

      It is exactly normal.

    Why

    With strongly skewed populations and small n, the CLT does not apply; x̄ is also skewed.

  4. Sample 4difficulty 3/5

    population x̄ for n=40

    The figure illustrates that a skewed population can produce

    • A

      A roughly normal sampling distribution of x̄ when n is large

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    • B

      A bimodal sampling distribution

    • C

      An equally skewed sampling distribution of x̄

    • D

      A uniform sampling distribution

    Why

    CLT: with large n, sampling distribution is approximately normal.

  5. Sample 5difficulty 3/5

    For a moderately skewed population, n =

    • A

      1

    • B

      1000+

    • C

      5

    • D

      30+

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    Why

    Conventional threshold; very heavily skewed populations may need larger n.