- A population is normally distributed with mean 50 and standard deviation 12. What is the probability that a sample of size 9 will have a mean between 48 and 52?
- The average price of gasoline at all U.S. gas stations was $3.00. Assume that the population standard deviation of gas prices is $1.75. We plan to take a random sample of 36 gas stations. What is the sampling distribution of x-bar?
- The average price of gasoline at all U.S. gas stations was $3.00. Assume that the population standard deviation of gas prices is $1.75. We plan to take a random sample of 16 gas stations. The sampling distribution of x-bar will be normal only if
- The average price of gasoline at all U.S. gas stations was $3.00 with a standard deviation of $1.75. Find the probability that a random sample of 36 gas stations will provide an average gas price that is more than $3.50.
- The average price of gasoline at all U.S. gas stations was $3.00 with a standard deviation of $1.75. Find the probability that a sample of 36 gas stations will provide an average gas price that is within $0.50 of the population mean.
- The probability in the preceding question would _______ if we were to increase the smaple size to 72.
- Census indicates that the proportion of adult women in the United States is 51%. We plan to take a random sample of 400 U.S. adults. What is the sampling distribution of p-bar?
- The critical value (CV) used for a 95% interval estimate is
- It is always better to have a 99% confidence interval than a 90% confidence interval
- A 95% confidence interval is wider than a 90% confidence interval
- A medical researcher would like to estimate the average height of 4th grade girls to within 1 inch. The standard deviation is known to be 4 inches. How many 4th grade girls must be measure to obtain a 98% confidence level?
- Which of the following will not result in a narrower confidence interval?
- If the p-value is larger than 10%, we assume that the null hypothesis is true.
- A company is considering increasing the workload of its employees because it feels they are not working a 40-hour week. Which pair of hypotheses should the company use to validate its position?
- Suppose the average household income in a certain city is $27,000 with a standard deviation of $5,500. What is the probability that a sample of 100 households will have a mean income of less than $26,000?
- In a poll 1000 American adults, 44% approve the job that Obama was doing handling the economy. The standard error is
- In a poll 1000 American adults, 44% approve the job that Obama was doing handling the economy. The critical value (CV) needed for 90% confidence interval estimation is
- In a poll 1000 American adults, 44% approve the job that Obama was doing handling the economy. The 90% confidence interval estimate is
- In a poll 1000 American adults, 44% approve the job that Obama was doing handling the economy. However, a political commentator claims that Obama's approval is 50%. In light of the sample evidence and at 10% level of significance