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Ch. 6 - Confidence Intervals
Larson - Elementary Statistics: Picturing the World 8th Edition
Larson8th EditionElementary Statistics: Picturing the WorldISBN: 9780137493470Not the one you use?Change textbook
Chapter 6, Problem 6.1.39

In Exercise 35, would it be unusual for the population mean to be over \$1500? Explain.

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Step 1: Identify the key components of the problem. The question is asking whether it would be unusual for the population mean to exceed \$1500. To determine this, we need to assess the probability of the population mean being greater than \$1500 using the concept of z-scores and the standard normal distribution.
Step 2: Recall the formula for the z-score for a population mean: z = (μ - μ0) / (σ / n), where μ is the population mean, μ0 is the hypothesized mean (in this case, \$1500), σ is the population standard deviation, and n is the sample size.
Step 3: Substitute the given values into the z-score formula. If the problem does not provide the population standard deviation (σ) or sample size (n), you will need to refer to Exercise 35 for these details.
Step 4: Use the z-score obtained to find the corresponding probability from the standard normal distribution table. This will give you the likelihood of the population mean being less than or equal to \$1500. To find the probability of the mean being greater than \$1500, subtract this value from 1.
Step 5: Interpret the result. If the probability of the population mean being greater than \$1500 is very small (commonly less than 0.05), it would be considered unusual for the population mean to exceed \$1500. Otherwise, it would not be unusual.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Population Mean

The population mean is the average of all values in a given population. It is a measure of central tendency that provides insight into the overall characteristics of the population. Understanding the population mean is crucial for determining how individual data points relate to the average, which can help assess whether a specific value, like $1500, is typical or unusual.
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Statistical Significance

Statistical significance refers to the likelihood that a result or relationship observed in data is not due to random chance. In the context of the population mean, determining whether a mean over $1500 is unusual involves assessing how far this value is from the expected mean and whether this deviation is statistically significant, often using hypothesis testing.
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Normal Distribution

Normal distribution is a probability distribution that is symmetric about the mean, indicating that data near the mean are more frequent in occurrence than data far from the mean. Many statistical analyses assume normality, and understanding this concept helps in evaluating whether a population mean over $1500 falls within a typical range or is an outlier, based on the distribution of the data.
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Related Practice
Textbook Question

Tennis Ball Manufacturing A company manufactures tennis balls. When the balls are dropped onto a concrete surface from a height of 100 inches, the company wants the mean bounce height to be 55.5 inches. This average is maintained by periodically testing random samples of 25 tennis balls. If the t-value falls between and , then the company will be satisfied that it is manufacturing acceptable tennis balls. For a random sample, the mean bounce height of the sample is 56.0 inches and the standard deviation is 0.25 inch. Assume the bounce heights are approximately normally distributed. Is the company making acceptable tennis balls? Explain.

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Textbook Question

Graphical Analysis In Exercises 9–12, use the values on the number line to find the sampling error.

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Textbook Question

Which statistic is the best unbiased estimator for μ?

a. s

b. xbar

c. the median

d. the mode

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Textbook Question

In Exercises 5–8, find the critical value zc necessary to construct a confidence interval at the level of confidence c.

c = 0.97

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Textbook Question

Drug Concentration You are analyzing the times for the drug concentrations to peak in the patients in Exercise 14. The population standard deviation of the times for epinephrine concentrations to peak should be less than 10 minutes. Does the confidence interval you constructed for σ suggest that the variation in the times is at an acceptable level? Explain your reasoning.

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Textbook Question

In Exercises 13–16, find the margin of error for the values of c, σ and n.

c = 0.95, σ = 5.2, n = 30

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