A study was commissioned to find the mean weight of the residents in certain town. The study examined a random sample of 36 residents and found the mean weight to be 182 pounds with a standard deviation of 29 pounds. Use the normal distribution/empirical rule to estimate a 95% confidence interval for the mean, rounding all values to the nearest tenth.
Q. A study was commissioned to find the mean weight of the residents in certain town. The study examined a random sample of 36 residents and found the mean weight to be 182 pounds with a standard deviation of 29 pounds. Use the normal distribution/empirical rule to estimate a 95% confidence interval for the mean, rounding all values to the nearest tenth.
Identify Data Parameters: Identify the sample mean, standard deviation, and sample size. The sample mean (xˉ) is given as 182 pounds, the standard deviation (σ) is 29 pounds, and the sample size (n) is 36 residents.
Calculate Standard Error: Determine the standard error of the mean (SEM). The standard error of the mean is calculated by dividing the standard deviation by the square root of the sample size. SEM=nσSEM=3629SEM=629SEM=4.8333... Rounded to the nearest tenth, SEM=4.8 pounds.
Find Z-Score for 95% Confidence: Find the z-score that corresponds to a 95% confidence level.For a 95% confidence interval, the z-score is typically 1.96 (this value comes from standard normal distribution tables).
Compute Margin of Error: Calculate the margin of error (ME). The margin of error is found by multiplying the z-score by the standard error of the mean. ME=z×SEMME=1.96×4.8ME=9.408 Rounded to the nearest tenth, ME=9.4 pounds.
Determine Confidence Interval: Determine the confidence interval.The confidence interval is calculated by adding and subtracting the margin of error from the sample mean.Lower limit = xˉ−MEUpper limit = xˉ+MELower limit = 182−9.4Upper limit = 182+9.4Lower limit = 172.6 poundsUpper limit = 191.4 pounds
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