Chapter 8: Interval Estimation

An estimate of a population parameter that provides an interval of values believed to contain the value of the parameter is known as the
1. confidence level
2. interval estimate
3. parameter level
4. population estimate
When estimating a population mean with a 95% confidence interval with a sample of size 20 that contains outliers
1. one should delete the outliers, giving a smaller sample size
2. one should increase the sample size
3. none of the above
If an interval estimate is said to be constructed at the 90% confidence level, the confidence coefficient would be
1. 0.1
2. 0.95
3. 0.9
4. none of the above
Whenever the population standard deviation is unknown and the population has a normal or near-normal distribution, which distribution is used in developing an interval estimation?
1. standard distribution
2. chi-square distribution
3. beta distribution
4. t-distribution
As the number of degrees of freedom in a t distribution increases, the difference between the t distribution and the standard normal distribution
1. becomes larger
2. becomes smaller
3. varies according to the confidence coefficient
4. none of the above
The t distribution is applicable whenever
1. the sample is considered small (n < 30)
2. the population is normal and the sample standard deviation is used to estimate the population standard deviation
3. both a and b
4. none of the above
In developing an interval estimate, if the population standard deviation is unknown
1. It is impossible to develop an interval estimate
2. the standard deviation is arrived at using historical data
3. the sample standard deviation can be used
4. none of the above
In order to estimate the average time spent on the computer terminals per student at a local university, data were collected from a sample of 81 business students over a one week period. Assume the population standard deviation is 1.2 hours. If the sample mean is 9 hours, then the 95% confidence interval is
1. 7.04 to 110.96 hours
2. 7.36 to 10.64 hours
3. 7.80 to 10.20 hours
4. 8.74 to 9.26 hours
5. none of the above
The confidence interval is also known as the
1. the standard error
2. interval estimate
3. confidence level
4. margin of error
The t value for a 95% confidence interval estimation with 28 degrees of freedom is
1. 2.467
2. 2.052
3. 2.048
4. 2.473
5. none of the above