Chapter 9: Business Statistics
If there is no estimate of the population proportion, what value should be used in calculating the sample size for a population proportion?
0.5
In choosing a sample size for a study, we need to know the population standard deviation. Which of the following could be used to estimate the population standard deviation? Select all that apply.
The sample standard deviation from a pilot study. The population standard deviation from a comparable study.
In creating a confidence interval for the population mean, if σ is unknown, we estimate it using which of the following?
s
A company has a total of 100 employees. From a random sample of 33 employees, the average age is found to be 44 years with a standard deviation of 3 years. Construct a 99% confidence interval to estimate the population mean age.
42.8 to 45.2
How does sample size affect the width of the confidence interval for the population mean?
Larger sample sizes result in narrower intervals.
How does the standard deviation of the population affect the width of the confidence interval for the population mean?
Larger values of the population standard deviation result in wider intervals.
The binomial conditions must be met before we can develop a confidence interval for a population proportion. Which two of the following are binomial conditions?
The probability of success is the same for all trials. We can define two outcomes, success and failure.
What is meant by the term "level of confidence"?
The probability that a parameter will be found within the confidence interval.
Which of the following formulas would you use to calculate the sample size for a mean? n = ?
(zσ/E)^2
A sample of size 25 is taken from a population with standard deviation 6. The sample mean is 10. Which of the following is a 99% confidence interval for the population mean?
6.9 to 13.1
In constructing a confidence interval to estimate the population mean from a sample, which of the following steps are necessary only when σ is not known? Select all that apply.
Find the sample standard deviation. Find the t-value for the proper distribution, based on the sample size.