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Business Statistics

Statistics

Quiz 8 :

Statistical Inference: Estimation for Single Populations

Quiz 8 :

Statistical Inference: Estimation for Single Populations

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A market researcher computed a confidence interval for a population proportion using a 95% confidence level.Her boss decided that she wanted a 99% confidence level instead.The new interval with 99% confidence level will be wider than the original one with a 95% confidence level.
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True False
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True

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If the population is normal and its standard deviation, σ, is known and the sample size, n, is large (n ≥ 30), interval estimates for the population mean must be determined using z-values.
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True False
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Answer:

True

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In determining the interval estimates for a population proportion using the sample proportion, it is appropriate to use the z-distribution.
Free
True False
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Answer:

True

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If the population is not normal but its standard deviation, σ is known and the sample size, n is large (n ≥ 30), z-distribution values may be used to determine interval estimates for the population mean.
True False
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A t-distribution is similar to a normal distribution, but with flatter tails.
True False
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In determining the interval estimates for a population variance using the sample variance, it is appropriate to use the values from a chi-square distribution rather than a t-distribution.
True False
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If the degrees of freedom in a t distribution increase, the difference between the t values and the z values will also increase.
True False
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When the population standard deviation, σ, is unknown the sample standard deviation, s, is used in determining the interval estimate for the population mean.
True False
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Use of the chi-square statistic to estimate the population variance is extremely robust to the assumption that the population is normally distributed.
True False
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In order to find values in the t distribution table, you must determine the appropriate degrees of freedom based on the sample sizes.
True False
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If the population is normal and its standard deviation, σ, is known but the sample size is small, z-distribution values may not be used to determine interval estimates for the population mean.
True False
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When a statistic calculated from sample data is used to estimate a population parameter, it is called a point estimate.
True False
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An assumption underlying the use of t-statistic in sample-based estimation is that the population is normally distributed.
True False
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Suppose a random sample of 16 is selected from a population with a normal distribution with a known population standard deviation σ of 10.Assume that the sample mean is 4.2.Based on a 90% confidence interval for the population mean, we can conclude that 0.1 is a plausible number for the population mean μ.
True False
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Catherine Chao, Director of Marketing Research, is evaluating consumer acceptance of a new toothpaste package.Her staff reports that 17% of a random sample of 200 households prefers the new package to all other package designs.If Catherine concludes that 17% of all households prefer the new package, she is using _______.
Multiple Choice
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Like a t-distribution, a chi-square distribution is symmetrical and extends from minus infinity to plus infinity.
True False
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When a range of values is used to estimate a population parameter, it is called a range estimate.
True False
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Given the error we are willing to tolerate, the sample size is determined by the mean, µ of the population and the confidence level.
True False
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You are thinking of using a t-table to find a 95 percent confidence interval for the mean μ of a population.The distribution of the population is normal and the population standard deviation is unknown.A random sample of size n is drawn from this population.You may use the t-distribution only if the sample size n is small.
True False
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In estimating the sample size necessary to estimate a population mean, the error of estimation, E, is equal to the difference between the sample mean and the sample standard deviation.
True False
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