Exam 8: Interval Estimation

A quality control technician is checking the weights of a product.She takes a random sample of 8 units and weighs each unit.The observed weights (in ounces) are shown below.Assume the population has a normal distribution. ​ Provide a 95% confidence interval for the mean weight of all such units.

In interval estimation, the t distribution is applicable only when the

A random sample of 64 SAT scores of students applying for merit scholarships showed an average of 1400 with a standard deviation of 240.If we want to provide a 95% confidence interval for the population mean SAT score, the degrees of freedom for reading the t value is

In order to estimate the average electric usage per month, a sample of 64houses was selected and the electric usage was determined.Assume a population standard deviation of 320 kilowatt-hours.At 95% confidence, the size of the margin of error is

A sample of 100 information systems managers had an average hourly income of $40.00 with a standard deviation of $8.00.If we want to determine a 95% confidence interval for the average hourly income of the population, the value of t is

Two hundred students are enrolled in an Economics class.After the first examination, a random sample of 6 papers was selected.The scores were 65, 75, 89, 71, 70, and 80. a. Determine the standard error of the mean. b. What assumption must be made before we can determine an interval for the mean score of all the students in the class? Explain why. c. Assume the assumption of Part b is met.Provide a 95% confidence interval for the mean score of all the students in the class.

In order to determine the summer unemployment rate among college students in a university, a pilot sample was taken; and it was determined that ten percent of the individuals in the sample were unemployed.Using the results of the pilot study and a 95% confidence, what sample size would be required to estimate the proportion of unemployed college students in the university if we want the margin of error not to exceed 3 percent?

When the level of confidence decreases, the margin of error

In order to determine how many hours per week freshmen college students watch television, a random sample of 256 students was selected.It was determined that the students in the sample spent an average of 14 hours with a standard deviation of 3.6 hours watching TV per week. a. Provide a 95% confidence interval estimate for the average number of hours that all college freshmen spend watching TV per week. b. Assume that a sample of 66 students was selected that resulted in the same mean and standard deviation.Provide a 95% confidence interval estimate for the average number of hours that all college freshmen spend watching TV per week. ​

The value added to and subtracted from a point estimate in order to develop an interval estimate of the population parameter is known as the

A random sample of 1000 people was taken.Seven hundred fifty of the people in the sample favored Candidate A.The 95% confidence interval for the true proportion of people who favor Candidate A is

A sample of 225 elements from a population with a standard deviation of 75 is selected.The sample mean is 180.The 98% confidence interval for μ is

The monthly incomes from a random sample of workers in a factory are shown below. ​ a. Compute the standard error of the mean (in dollars). b. Compute the margin of error (in dollars) at 95% confidence. c. Compute a 95% confidence interval for the mean of the population.Assume the population has a normal distribution.Give your answer in dollars. ​

In order to determine an interval for the mean of a population with unknown standard deviation, a sample of 58 items is selected.The mean of the sample is determined to be 36.The associated number of degrees of freedom for reading the t value is

The t value for a 95% confidence interval estimation with 96 degrees of freedom is

For the interval estimation of μ when σ is known and the sample is large, the proper distribution to use is the

In a random sample of 144 observations, = .7.The 95% confidence interval for p is

The following random sample from a population whose values were normally distributed was collected. ​ The 95% confidence interval for μ is

From a population with a variance of 484, a sample of 256 items is selected.At 95% confidence, the margin of error is

A sample of 100 information systems managers had an average hourly income of $40.00 with a standard deviation of $8.00.The standard error of the mean is