8.1 Estimation Using Normal

# 42 and 36818 grams using ms excel interval estimation

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Unformatted text preview: grams—determine interval estimate Standard deviation σ = 15 grams Sampling distribution for Sample Size n = 25: ◦ Normal distribution (population follows normal distribution): Interval Estimation Sample mean = 362.3 grams (given in problem) Standard error of the mean: σ =σ = 3 x 2 5 Confidence Interval ◦ . 3. 9 8 margin of error is 5.88: z σ z531 ⋅ = 8 α x=02 = 6 5 2 0 . ◦ therefore, interval is ◦ 3 23 58 6. ± . 8 Interval Estimate 3 64 ≤µ 3 81 5. 2 ≤ 6. 8 Given a sample mean of 362.3, we can be 95% confident that the population mean is between 356.42 and 368.18 grams. Using MS Excel Interval Estimation =CONFIDENCE.NORM(alpha,standard_dev,size) Returns the margin of error that you can use to construct a confidence interval for a population mean. The confidence interval is a range of values. Your sample mean, x, is at the center of this range and the range is x ± CONFIDENCE.NORM Note: alpha—level of significance standard_dev—standard deviation of population (not standard error of the mean) size—sample size Using MS Excel Interval Estimation =CONFIDENCE.NORM(alpha,standard_dev,size) Returns the margin of error that you can use to construct a confidence interval for a population mean. The confidence interval is a range of values. Your sample mean, x, is at the center of this range and the range is x ± CONFIDENCE.NORM Note: alpha—level of significance SAFETY CHECK: CONFIDENCE.NORM can standard_dev—standard deviation of population only (not standard error of the mean) be used for finding the margin of error for a population size—sample size mean when the standard deviation is known. σ Known Example If the sample mean is found to be 362.3, find the 95% confidence interval (i.e., interval estimate) for the population mean. Population distribution: ◦ Normal distribution: Mean μ = ? grams—determine interval estimate Standard deviation σ = 15 grams Sampling distribution for Sample Size n = 25: ◦ Normal distribution (population follow...
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