Mathematics

Question

You are told that in a sample of size 225 the mean is 48.5 and the standard deviation is 1.8. The study is reported with 90% confidence level. Explain how to determine if 48.8 is within the confidence interval.

CL(%); 90, 95, 99
z*score:1.645, 1.96, 2.58

2 Answer

  • To find the margin of error, multiply the z-score by the standard deviation, then divide by the square root of the sample size.The z*-score for a 90% confidence level is 1.645.The margin of error is 0.20.The confidence interval is 48.3 to 48.7.48.8 is not within the confidence interval. 

  • To find the margin of error, multiply the z-score by the standard deviation, then divide by the square root of the sample size.

    The z*-score for a 90% confidence level is 1.645.The margin of error is 0.20.

    The confidence interval is 48.3 to 48.7.

    48.8 is not within the confidence interval.

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