Confidence Interval

A sample mean is the best point estimate of _______.

• A. The population standard deviation

• B. The population median

• C. The population mean

• D. The sample standard deviation

A sample standard deviation is the best point estimate of the ___________.

• A. Population range

• B. Population skewness

• C. Population mode

• D. Population standard deviation

A confidence interval for a population mean __________.

• A. Estimates the population range

• B. Estimates a likely interval for a population mean

• C. Estimates likelihood or probability

• D. Estimates the population standard deviation

Knowing the population standard deviation, a 95% confidence interval infers that the

population mean ___________.

• A. Is between 0 and 100%

• B. Is within ±1.96 standard deviations of the sample mean

• C. Is within ±1.96 standard errors of the sample mean

• D. Is too large

When a confidence interval for a population mean is constructed from sample data,

__________.

• A. We can conclude that the population mean is in the interv

• B. We can conclude that the population mean is not in the interval

• C. We can conclude, for an infinite number of samples and corresponding confidence

  intervals, that the population mean is in a stated percentage of the intervals

• D. We cannot make any inferences

The distribution of Student's t is ________.

• A. Symmetrical

• B. Negatively skewed

• C. Positively skewed

• D. A discrete probability distribution

When using Student's t to compute an interval estimate, ___________.

• A. We assume that the samples are collected from populations that are uniformly

  distributed

• B. We estimate the population mean based on the sample mean

• C. We use the z distribution

• D. We assume that the samples are collected from normally distributed populations

A random sample of 42 college graduates revealed that they worked an average of 5.5

years on the job before being promoted. The sample standard deviation was 1.1 years.

Using the 0.99 degree of confidence, what is the confidence interval for the population

mean?

• A. 5.04 and 5.96

• B. 5.06 and 5.94

• C. 2.67 and 8.33

• D. 4.40 and 6.60

When we use a confidence interval to reach a conclusion about the population mean, we

are applying a type of reasoning or logic called __________.

• A. Descriptive statistics

• B. The normal distribution

• C. Statistical inference

• D. Graphics

A university surveyed recent graduates of the English Department for their starting

salaries. Four hundred graduates returned the survey. The average salary was $25,000,

with a standard deviation of $2,500. What is the best point estimate of the population

mean?

• A. $25,000

• B. $2,500

• C. $400

• D. $62.5