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    A common problem in inferential statistics is constructing a confidence interval.

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    The makers of a soft drink want to identify the average age of its consumers. A sample of 16 consumers is taken. The average age in the sample was 22.5 years with a standard deviation of 5 years.
    1. Construct a 95% confidence level.
    2. Now do the same thing with 80% confidence level.

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    https://brainmass.com/statistics/confidence-interval/inferential-statistics-constructing-confidence-interval-3246

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    Part One (for 95% confidence interval):

    1. Calculate the estimated standard error of the mean ('SEM'):

    SEM = standard deviation / square root ('SQRT') of sample size = 5 / SQRT(16) = 1.25

    2. Calculate df:

    df = n-1 = 16-1 = 15

    3. Determine t value for 95% confidence:

    Use Student's t distribution table to determine t, using df =15 ...

    Solution Summary

    The solution addresses the makers of a soft drink want to identify the average age of its consumers. A sample of 16 consumers is taken. The average age in the sample was 22.5 years with a standard deviation of 5 years.
    1. Construct a 95% confidence level.
    2. Now do the same thing with 80% confidence level.

    $2.19

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