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Why is obtaining the mean and standard deviation of x¯ a first step in approximating the sample distribution of the sample mean by a normal distribution?

Short Answer

Expert verified

The normal distribution always depends upon two parameters the mean and the standard deviation for any given random variable. Hence, the mean and standard deviation of x¯are obtained first when approximating the sample distribution of the sample mean by a normal distribution.

Step by step solution

01

Step 1. Given Information

The objective is to find the reason why obtaining the mean and standard deviation of x¯is a first step in approximating the sampling distribution of the sample mean by a normal distribution.

02

Step 2. Explanation

A variable is normally distributed if its distribution has the shape of a normal curve and that a normal distribution is determined by the mean and standard deviation.

Hence a first step in learning how to approximate the sampling distribution of the sample mean by a normal distribution is to obtain the mean and standard deviation of the sample mean, that is, of the variable x¯.

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Most popular questions from this chapter

Population data: 2,3,5,7,8

Part (a): Find the mean, μ, of the variable.

Part (b): For each of the possible sample sizes, construct a table similar to Table 7.2on the page localid="1652592045497" 293and draw a dotplot for the sampling for the sampling distribution of the sample mean similar to Fig 7.1on page 293.

Part (c): Construct a graph similar to Fig 7.3and interpret your results.

Part (d): For each of the possible sample sizes, find the probability that the sample mean will equal the population mean.

Part (e): For each of the possible sample sizes, find the probability that the sampling error made in estimating the population mean by the sample mean will be 0.5or less, that is, that the absolute value of the difference between the sample mean and the population mean is at most0.5.

America's Riches. Each year, Forbes magazine publishes a list of the richest people in the United States. As of September l6, 2013, the six richest Americans and their wealth (to the neatest billion dollars) are as shown in the following table. Consider these six people a population of interest.

(a) For sample size of 5construct a table similar to table 7.2 on page293.(There are 6 possible sample) of size 5

(b) For a random sample of size 5determine the probability that themean wealth of the two people obtained will be within 3(i.e,3billion) of the population mean. interpret your result in terms of percentages.

7.51 Earthquakes. According to The Earth: Structure, Composition and Evolution (The Open University, S237), for earthquakes with a magnitude of 7.5or greater on the Richter scale, the time between successive earthquakes has a mean of 437days and a standard deviation of 399days. Suppose that you observe a sample of four times between successive earthquakes that have a magnitude of 7.5 or greater on the Richter scale.
a. On average, what would you expect to be the mean of the four times?
b. How much variation would you expect from your answer in part (a)? (Hint: Use the three-standard-deviations rule.)

Suppose that a sample is to be taken without replacement from a finite population of size Nif the sample size is the same as the population size

(a) How many possible samples are there?

(b) What are the possible sample means?

(c) What is the relationship between the only possible sample and the population

Provide two synonyms for the distribution of all possible sample means for samples of a given size.

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