1.) From a sample of 500 items, 380 were found to be non-defective. The point estimate of the population proportion of defectives will be:

2.)A marketing research consultant hired by Coca-Cola is interested in determining the proportion of customers who favor Coke over other soft drinks. A random sample of 400 consumers was selected from the market under investigation and showed that 53% favored Coca-Cola over other brands. A 80% confidence interval for the true proportion of people who favor Coke is:

3.) A department store is interested in the average balance that is carried on its store’s credit card. A sample of 40 accounts reveals an average balance of $1,250 and a standard deviation of $350. Find a 95% confidence interval for the mean account balance on this store’s credit card:

4.) For sampling from a population that has a standard deviation of 200, what sample size would be needed to obtain a 95% confidence interval with width no more than 50?

5.) What is the correct Excel 2010 formula to calculate the upper tail z-score in obtaining 99% confidence interval of a population parameter?

6.) A 95% confidence interval for a population mean based on a sample has been calculated to be (20 , 30). We then double the sample size and calculate the 95% confidence interval based on the new sample. Which of the following can be a possible confidence interval?

7.) If we plot two normal probability distributions which have the same mean, the one which has a lower standard deviation will look :

8.) The opportunity for sampling error is decreased by

Subject | Mathematics |

Due By (Pacific Time) | 07/22/2014 06:30 pm |

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