A study by the department of education of a certain state was trying to determine the mean SAT scores of the graduating high school seniors. The study examined the scores of a random sample of 212 graduating seniors and found the mean score to be 489 with a standard deviation of 107 . 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 by the department of education of a certain state was trying to determine the mean SAT scores of the graduating high school seniors. The study examined the scores of a random sample of 212 graduating seniors and found the mean score to be 489 with a standard deviation of 107 . Use the normal distribution/empirical rule to estimate a 95\% confidence interval for the mean, rounding all values to the nearest tenth.
Identify given information: Identify the given information.We have a sample mean (xˉ) of 489, a standard deviation (σ) of 107, and a sample size (n) of 212. We want to estimate the 95% confidence interval for the population mean.
Determine z-score: Determine the z-score that corresponds to a 95% confidence level.For a 95% confidence interval, the z-score that corresponds to the middle 95% of the normal distribution is approximately 1.96. This value can be found in standard z-score tables or by using a calculator that provides the z-score for a given confidence level.
Calculate SEM: Calculate 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=212107
Calculate standard error: Perform the calculation for the standard error of the mean. SEM=212107SEM≈14.56107SEM≈7.35 (rounded to the nearest tenth)
Calculate margin of error: Calculate the margin of error (ME) for the confidence interval.The margin of error is found by multiplying the z-score by the standard error of the mean.ME=z×SEMME=1.96×7.35
Calculate lower and upper bounds: Perform the calculation for the margin of error.ME=1.96×7.35ME≈14.41 (rounded to the nearest tenth)
Calculate lower and upper bounds: Perform the calculation for the margin of error.ME=1.96×7.35ME≈14.41 (rounded to the nearest tenth)Calculate the lower and upper bounds of the 95% confidence interval.Lower bound = xˉ−MEUpper bound = xˉ+MELower bound = 489−14.41Upper bound = 489+14.41
Calculate lower and upper bounds: Perform the calculation for the margin of error.ME=1.96×7.35ME≈14.41 (rounded to the nearest tenth)Calculate the lower and upper bounds of the 95% confidence interval.Lower bound = xˉ−MEUpper bound = xˉ+MELower bound = 489−14.41Upper bound = 489+14.41Perform the calculations for the lower and upper bounds.Lower bound ≈489−14.41Lower bound ≈474.6 (rounded to the nearest tenth)Upper bound ≈489+14.41Upper bound ≈503.4 (rounded to the nearest tenth)
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