CI for Mean known st. deviation
The critical value (z-score) for a 99% confidence interval when the population standard deviation is known
What is 2.58
Given that 90 out of 200 adults were smokers, find the point estimate for the population proportion of adults who are smokers. Be sure to attach a symbol to it.
What is p-hat = 0.45
What distribution must be used when computing confidence intervals for variances and standard deviations.
What is Chi-square
A confidence interval is an _____________________ for a population parameter.
What is "interval estimate".
When a 99% confidence interval is calculated instead of a 95% CI with n being the same, the margin of error will be a) larger b) smaller c) the same d) cannot be determined
What is a) larger
An irate patient complained that the cost of a doctor's visit was too high. She randomly surveyed 20 other patients and found that the mean amount of money they spent on each doctor's visit was $44.80 with a standard deviation of $3.53. What assumption must be made in order to construct a 95% CI for the population mean?
What is "normally distributed".
Find p-hat (proportion of lefties) and q-hat given that 16 out of 130 people were lefties.
What is 0.12 and 0.88
Find the left and right Chi-square values for a 99% CI with a sample size of 6
What is 0.412 and 16.750
You are running a political campaign and wish to estimate, with 98% confidence, the proportion of registered voters who will vote for your candidate. Your estimate must be accurate within 2% of the true population. Find the minimum sample size needed.
What is 3394 registered voters.
A random sample of 49 shoppers showed that they spend an average of $23.45 per visit at the Saturday Mornings Bookstore. The standard deviation of the population is $2.80 Find the 90% CI of the true mean.
What is $22.79 < u < $24.11
An irate patient complained that the cost of a doctor's visit was too high. She randomly surveyed 20 other patients and found that the mean amount of money they spent on each doctor's visit was $44.80 with a standard deviation of $3.53. Assume the population is normally distributed. Find the 95% CI of the population mean.
What is $43.15 < u < $46.45
A recent study of 75 workers found that 53 people rode the bus to work each day. Find the 95% CI for the proportion of all workers of all workers who rode the bus to work.
What is 0.604 < p < 0.810
Find the left and right Chi-square values for a 90% CI with a sample size of 50
What is 26.509 and 55.758 (use df = 40)
A business wants to estimate the mean age of its customers. If they want to be 90% confident that the sample mean is within 1/2 year of the population mean, what is the minimum sample size the company should use? Assume the population standard deviation is about 8 years.
What is 689.
The average weight of 40 randomly selected mini-vans was 4150 pounds. The population standard deviation was 480 pounds. Find the 99% CI of the population mean weight of the minivans. Round final answers to the nearest tenth.
What is 3954.2 < u < 4345.8
In a hospital, a sample of 8 weeks found that an average of 438 patients was treated in the emergency room each week, and the standard deviation was 16 patients. Find the 99% CI for the true mean.
What is "this problem can't be worked because n is less than 30 and we don't know that the weekly number of ER patients is normally distributed"?
In a study of 150 accidents that required treatment in an emergency room, 36% involved children under 6 years of age. Find the 90% CI of the true proportion of accidents that involve children under the age of 6. Round final answers to 3 decimal places.
What is 0.296 < p < 0.424?
A sample of 25 novels has a standard deviation of 9 pages. Find the 95% CI of the population standard deviation. Assume the number of pages is normally distributed.
What is 7.0 < o < 12.5
A sample of 1200 adults yielded a confidence interval of (0.685, 0.735) for the population proportion. To the nearest tenth of a percent, find the level of confidence.
What is 94.4%.