ISDS CH 8
Why is it not possible to have 100% confidence? Explain
A 100% confidence interval is not possible unless either the entire population is sampled or an absurdly wide interval of estimates is provided
What does your answer to (a) tell you about the "practicality" of using the confidence interval estimate formula?
If you have a sample, you are computing the sample standard deviation needed in confidence interval estimate formula. If you have a population and have computed the population mean and population standard deviation, you don't need a confidence interval estimate of the population mean`
A 90 confidence interval estimate for the population mean paper length is 10.9957110.99571less than or equals≤muμless than or equals≤11.0022911.00229. Is it true that you do not know for sure whether the population mean is between 10.9957110.99571 and 11.0022911.00229 inches? Explain
It is true because the population mean will be in the interval only 9090% of the time.
A market researcher selects a simple random sample of nequals=100 users of a social media website from a population of over 100 million registered users. After analyzing the sample, she states that she has 95% confidence that the mean time spent on the site per day is between 15 and 57 minutes. Explain the meaning of this statement
One is 95% confident that the true mean time all registered users spend on the site per day is between 15 and 57 minutes.
A market researcher collects a simple random sample of customers from its population of two million customers. After analyzing the sample, she states that she has 95% confidence that the mean annual income of its two million customers is between $ 56 comma 000$56,000 and $ 72 comma 000.$72,000. Suppose that the population mean annual income is $ 62 comma 000.$62,000. Is the confidence interval estimate correct? Explain
Yes, because the value of muμ isis included within the confidence interval estimate.
Which statistical measure would you compute first, the mean or the standard deviation? Explain. Choose the correct answer below.
You would compute the mean first because it is needed in order to compute the standard deviation. If you had a sample, you would compute the sample mean. If you had the population mean, you would compute the population standard deviation