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Ch. 6 - Confidence Intervals
Larson - Elementary Statistics: Picturing the World 8th Edition
Larson8th EditionElementary Statistics: Picturing the WorldISBN: 9780137493470당신이 사용하는 게 아니라요?교과서 변경
6장, 문제 6.2.25b

Constructing a Confidence Interval In Exercises 25–28, use the data set to (b) find the sample standard deviation. Assume the population is normally distributed.
SAT Scores The SAT scores of 12 randomly selected high school seniors
Table displaying SAT scores of 12 randomly selected high school seniors in two rows.

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Step 1: Write down the SAT scores provided in the data set: {1130, 1290, 1010, 1320, 950, 1250, 1340, 1100, 1260, 1180, 1470, 920}.
Step 2: Calculate the mean (average) of the data set using the formula: \( \text{Mean} = \frac{\sum x_i}{n} \), where \( x_i \) represents each individual score and \( n \) is the total number of scores.
Step 3: Compute the squared differences from the mean for each score using the formula: \( (x_i - \text{Mean})^2 \).
Step 4: Find the variance by summing all the squared differences and dividing by \( n-1 \) (since this is a sample, not a population): \( \text{Variance} = \frac{\sum (x_i - \text{Mean})^2}{n-1} \).
Step 5: Calculate the sample standard deviation by taking the square root of the variance: \( \text{Standard Deviation} = \sqrt{\text{Variance}} \).

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주요 개념

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Sample Standard Deviation

The sample standard deviation is a measure of the amount of variation or dispersion in a set of sample data points. It quantifies how much the individual scores differ from the sample mean. To calculate it, you take the square root of the variance, which is the average of the squared differences from the mean. This concept is crucial for understanding the spread of SAT scores in the given data set.
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Calculating Standard Deviation

Normal Distribution

Normal distribution is a probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean. In statistics, many tests and confidence intervals assume that the underlying data is normally distributed, which simplifies analysis and interpretation. This assumption is important when constructing confidence intervals for the SAT scores.
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가이드 코스
06:23
Using the Normal Distribution to Approximate Binomial Probabilities

Confidence Interval

A confidence interval is a range of values, derived from a data set, that is likely to contain the true population parameter with a specified level of confidence, typically 95% or 99%. It provides an estimate of uncertainty around a sample statistic, such as the mean. Understanding how to construct and interpret confidence intervals is essential for making inferences about the population based on the sample data provided.
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가이드 코스
06:33
Introduction to Confidence Intervals
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교과서 질문

Constructing Confidence Intervals In Exercises 13–24, assume the sample is from a normally distributed population and construct the indicated confidence intervals for (b) the population standard deviation σ. Interpret the results.

[APPLET] Earnings The annual earnings (in thousands of dollars) of 21 randomly selected level 1 computer hardware engineers are listed. Use a 99% level of confidence. (Adapted from Salary.com)

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교과서 질문

Constructing a Confidence Interval In Exercises 25–28, use the data set to (c) construct a 99% confidence interval for the population mean. Assume the population is normally distributed.

SAT Scores The SAT scores of 12 randomly selected high school seniors

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교과서 질문

Senate Filibuster You wish to estimate, with 99% confidence, the population proportion of U.S. adults who disapprove of the U.S Senate’s use of the filibuster. Your estimate must be accurate within 2% of the population proportion.

b. Find the minimum sample size needed, using a prior survey that found that 34% of U.S. adults disapprove of the U.S Senate’s use of the filibuster. (Source: Monmouth University)

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교과서 질문

Constructing Confidence Intervals In Exercises 13–24, assume the sample is from a normally distributed population and construct the indicated confidence intervals for (b) the population standard deviation σ. Interpret the results.

Drive-Thru Times The times (in seconds) spent by a random sample of 28 customers in the drive-thru of a fast-food restaurant have a sample standard deviation of 56.1. Use a 98% level of confidence.

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교과서 질문

Constructing a Confidence Interval In Exercises 25–28, use the data set to (c) construct a 99% confidence interval for the population mean. Assume the population is normally distributed.

Homework The weekly time spent (in hours) on homework for 18 randomly selected high school students

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교과서 질문

Constructing Confidence Intervals In Exercises 13–24, assume the sample is from a normally distributed population and construct the indicated confidence intervals for (b) the population standard deviation σ. Interpret the results.

Annual Precipitation The annual precipitation amounts (in inches) of a random sample of 61 years for Chicago, Illinois, have a sample standard deviation of 6.46. Use a 98% level of confidence. (Source: National Oceanic and Atmospheric Administration)

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