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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 6.2.13

In Exercises 13 and 14, use the confidence interval to find the margin of error and the sample mean.
(14.7, 22.1)

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Step 1: Understand the problem. The confidence interval is given as (14.7, 22.1). The goal is to find the margin of error and the sample mean. The confidence interval represents the range of values within which the true population parameter is expected to lie.
Step 2: Recall the formula for the margin of error. The margin of error (E) is half the width of the confidence interval. Mathematically, it is calculated as: E = \(\frac{\text{Upper Limit}\) - \(\text{Lower Limit}\)}{2}.
Step 3: Recall the formula for the sample mean. The sample mean (\(\bar{x}\)) is the midpoint of the confidence interval. Mathematically, it is calculated as: \(\bar{x}\) = \(\frac{\text{Upper Limit}\) + \(\text{Lower Limit}\)}{2}.
Step 4: Substitute the given values into the formulas. For the margin of error, substitute 22.1 as the upper limit and 14.7 as the lower limit into the formula for E. For the sample mean, substitute the same values into the formula for \(\bar{x}\).
Step 5: Simplify the expressions to find the numerical values of the margin of error and the sample mean. This will give you the final results.

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주요 개념

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Confidence Interval

A confidence interval is a range of values, derived from sample statistics, that is likely to contain the true population parameter. It is expressed as an interval (e.g., (14.7, 22.1)) and is associated with a confidence level, typically 95% or 99%. This means that if we were to take many samples and build intervals in this way, a certain percentage of them would contain the true parameter.
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가이드 코스
06:33
Introduction to Confidence Intervals

Margin of Error

The margin of error quantifies the uncertainty associated with a sample estimate. It is calculated as half the width of the confidence interval, representing the maximum expected difference between the sample statistic and the population parameter. In the given interval (14.7, 22.1), the margin of error would be (22.1 - 14.7) / 2 = 3.7.
추천 영상:
가이드 코스
04:08
Finding the Minimum Sample Size Needed for a Confidence Interval

Sample Mean

The sample mean is the average of a set of values obtained from a sample, serving as an estimate of the population mean. It is calculated by summing all sample values and dividing by the number of observations. In the context of the confidence interval, the sample mean can be found as the midpoint of the interval, which is (14.7 + 22.1) / 2 = 18.4.
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가이드 코스
05:11
Sampling Distribution of Sample Proportion
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In Exercises 9–12, construct the indicated confidence interval for the population mean μ using the t-distribution. Assume the population is normally distributed.

c = 0.98, xbar = 4.3, s = 0.34, n = 14

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교과서 질문

Matching In Exercises 17–20, match the level of confidence c with the appropriate confidence interval. Assume each confidence interval is constructed for the same sample statistics.

c = 0.88

101
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교과서 질문

In Exercises 29–32, determine the minimum sample size n needed to estimate for the values of c, σ, and E.

c = 0.90, σ = 6.8, E = 1.

148
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교과서 질문

Translating Statements In Exercises 29–34, translate the statement into a confidence interval. Approximate the level of confidence.

In a survey of 220 U.S. adults ages 18–29, 65% said that they use Snapchat. The survey’s margin of error is ±7.9%. (Source: Pew Research Center)

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교과서 질문

In Exercises 35–40, use the standard normal distribution or the t-distribution to construct a 95% confidence interval for the population mean. Justify your decision. If neither distribution can be used, explain why. Interpret the results.

In a random sample of 18 months from January 2011 through December 2020, the mean interest rate for 30-year fixed rate home mortgages was 3.95% and the standard deviation was 0.49%. Assume the interest rates are normally distributed. (Source: Freddie Mac)

101
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교과서 질문

Finding Critical Values for χ2 In Exercises 3–8, find the critical values χR2 and χL2 for the level of confidence c and sample size n.

c = 0.80, n = 51

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