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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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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

What is the sampling distribution of a statistic? Why is it important?

Consider simple random samples of size n without replacement from a population of size N.

Part (a): Show that if n≤0.05N,then0.97≤N-nN-1≤1,

Part (b): Use part (a) to explain why there is little difference in the values provided by Equations (7.1)and (7.2)when the sample size is small relative to the population size- that is, when the size of the sample does not exceed 5% of the size of the population.

Part (c): Explain why the finite population correction factor can be ignored and the simpler formula, Equation (7.2), can be used when the sample size is small relative to the population size.

Part (d): The term N-n/N-1is known as the finite population correction factor. Can you explain why?

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