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  • When to use a z-interval?

    • Population standard deviation (σ) is known

    • Sample is random

    • Population is normal OR sample size is large

  • x̅

    Sample Mean

  • Z*

    Critical Value

  • (σ)

    Population Standard Deviation

  • n

    Sample Size

  • High Confidence Level

    Larger margin of error

  • Larger Sample Size

    Small margin of error

  • small standard deviation

    small margin error

  • ME=z* (σ/√n)

    Margin of error formula

  • How to Reduce Margin of Error

    • Increase sample size

    • Lower the confidence level

  • Use a t-interval when:

    • Population standard deviation is unknown

    • Use sample standard deviation (s)

    • Population is approximately normal OR sample size is large

  • Null Hypothesis

    Ho

  • Alternative Hypothesis

    Ha

  • Check Conditions:

    Random Sample

    Independent variable

    Large counts condition