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Suppose that the average grade for all people who take this course in statistics is 83 with a standard deviation of 3.5. If your particular class has an average of 89, can you conclude that your class is better than average at the 90 percent confidence level? Sample size 21.

Identify one or two-tailed
States the Null and Alternative Hypothesis
States the Level of Significance
Calculates Test Statistic
Formulates Decision Rule
Makes a Conclusion

  • Statistics - ,

    Null hypothesis:
    Ho: µ = 83 -->meaning: population mean is equal to 83
    Ha: µ does not equal 83 -->meaning: population does not equal 83

    Since the problem is using confidence intervals, remember that 5% (or .05) will be below the interval and 5% (or .05) will be above the interval. This will be a two-tailed test.

    Using the z-test formula to find the test statistic:
    z = (sample mean - population mean)/(standard deviation divided by the square root of the sample size)
    z = (89 - 83)/(3.5/√21)
    Finish the calculation.

    Determine whether or not to reject the null. If you reject the null, you will conclude a difference.

    I hope this will help get you started.

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