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## Quiz 8 : Statistical Inference: Estimation for Single Populations

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.
Free
True False

True

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.
Free
True False

True

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

True

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
A t-distribution is similar to a normal distribution, but with flatter tails.
True False
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
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
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
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
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
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
When a statistic calculated from sample data is used to estimate a population parameter, it is called a point estimate.
True False
An assumption underlying the use of t-statistic in sample-based estimation is that the population is normally distributed.
True False
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
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
Like a t-distribution, a chi-square distribution is symmetrical and extends from minus infinity to plus infinity.
True False