What important theorem in statistics implies that, for a large sample size, the possible sample proportions of that size have approximately a normal distribution?

Short Answer

Expert verified

The central limit theorem is a statistician's theorem that states that with a large sample size, the conceivable sample proportions have a normal distribution.

Step by step solution

01

Given Information

The various sample proportions of large sample size have an essentially normal distribution.

02

Explanation

In statistics, the central limit theorem is one of the most significant and extensively used theorems.

This theorem states that if the sample size is high enough, the sampling distribution of that proportion will be close to a normal distribution, regardless of whether the variable under discussion has a skewed or normal distribution. The theorem is valid even for smaller samples if the population is normal.

Values of a variable in a population can follow several probability distributions, such as left-skewed, right-skewed, normal, uniform, and so on. The central limit theorem applies to variables that are both independently and identically distributed. This indicates that the worth of one sample observation should not be influenced by the worth of another.

In addition, the sample size necessary for an essentially normal distribution is influenced by the fact that many shapes of the variable in the underlying population are not normal. This means that the central limit theorem demands a bigger sample size if the variable is substantially skewed in the population.

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Most popular questions from this chapter

a. Determine the sample proportion.

b. Decide whether using the one-proportion z-test is appropriate.

c. If appropriate, use the one-proportion z-test to perform the specified hypothesis test.

x=10

n=40

role="math" localid="1651300220980" H0:p=0.3

Ha:p<0.3

role="math" localid="1651300430510" α=0.05

In this Exercise, we have given the number of successes and the sample size for a simple random sample from a population. In each case,

a. use the one-proportion plus-four z-interval procedure to find the required confidence interval.

b. compare your result with the corresponding confidence interval found in Exercises 11.25-11.30, if finding such a confidence interval was appropriate.

x=40,n=50,95%level

Fill in the blanks.

a. The mean of all possible sample proportions is equal to the

b. For large samples, the possible sample proportions have approximately a distribution.

c. A rule of thumb for using a normal distribution to approximate the distribution of all possible sample proportions is that both and are or greater.

we have given a likely range for the observed value of a sample proportionp^

0.4to0.7

a. Based on the given range, identify the educated guess that should be used for the observed value of p^to calculate the required sample size for a prescribed confidence level and margin of error.

b. Identify the observed values of the sample proportion that will yield a larger margin of error than the one specified if the educated guess is used for the sample-size computation.

In discussing the sample size required for obtaining a confidence interval with a prescribed confidence level and margin of error, we made the following statement: "... we should be aware that, if the observed value of p^is closer to 0.5than is our educated guess, the margin of error will be larger than desired." Explain why.

One-Proportion Plus-Four z-Interval Procedure. To obtain a plus four z-interval for a population proportion, we first add two successes and two failures to our data (hence, the term "plus four") and then apply Procedure 11.1on page 454to the new data. In other words, in place of p^(which is x/n), we use p~=(x+2)/(n+4). Consequently, for a confidence level of 1-α, the endpoints of the plus-four z-interval are

p~±za/2·p~(1-p~)/(n+4)

As a rule of thumb, the one-proportion plus-four z-interval procedure should be used only with confidence levels of 90% or greater and sample sizes of 10 or more.

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