Exam 8: Interval Estimation

From a population that is normally distributed, a sample of 25 elements is selected and the standard deviation of the sample is computed. For the interval estimation of μ, the proper distribution to use is the

If we want to provide a 95% confidence interval for the mean of a population, the confidence coefficient is

For which of the following values of P is the value of P1 - P) maximized?

In order to estimate the average electric usage per month, a sample of 196 houses was selected, and their electric usage determined. a. Assume a population standard deviation of 350-kilowatt hours. Determine the standard error of the mean. b. With a 0.95 probability, determine the margin of error. c. If the sample mean is 2,000 KWH, what is the 95% confidence interval estimate of the population mean?

In general, higher confidence levels provide

Exhibit 8-2 A random sample of 121 automobiles traveling on an interstate showed an average speed of 65 mph. From past information, it is known that the standard deviation of the population is 22 mph. -Refer to Exhibit 8-2. The 96.6% confidence interval for μ is

A simple random sample of 144 items resulted in a sample mean of 1257.85 and a standard deviation of 480. Develop a 95% confidence interval for the population mean.

A random sample of 64 students at a university showed an average age of 25 years and a sample standard deviation of 2 years. The 98% confidence interval for the true average age of all students in the university is

When s is used to estimate σ, the margin of error is computed by using

The manager of a grocery store wants to determine what proportion of people who enter his store are his regular customers. What size sample should he take so that at 97% confidence the margin of error will not be more than 0.1?

Exhibit 8-2 A random sample of 121 automobiles traveling on an interstate showed an average speed of 65 mph. From past information, it is known that the standard deviation of the population is 22 mph. -Refer to Exhibit 8-2. The standard error of the mean is

You are given the following information obtained from a sample of 5 observations taken from a population that has a normal distribution. 94 72 93 54 77 Develop a 98% confidence interval estimate for the mean of the population.

In a random sample of 144 observations, = 0.6. The 95% confidence interval for P is

You are given the following information obtained from a random sample of 6 observations. Assume the population has a normal distribution. 14 20 21 16 18 19 a. What is the point estimate of μ? b. Construct an 80% confidence interval for μ. c. Construct a 98% confidence interval for μ. d. Discuss why the 80% and 98% confidence intervals are different.

The average monthly electric bill of a random sample of 256 residents of a city is $90 with a standard deviation of $24. a. Construct a 90% confidence interval for the mean monthly electric bills of all residents. b. Construct a 95% confidence interval for the mean monthly electric bills of all residents.

In a random sample of 400 residents of Chattanooga, 320 residents indicated that they voted for the Democratic candidate in the last presidential election. Develop a 95% confidence interval estimate for the proportion of all Chattanooga residents who voted for the Democratic candidate.

The Highway Safety Department wants to study the driving habits of individuals. A sample of 121 cars traveling on the highway revealed an average speed of 60 miles per hour with a standard deviation of 11 miles per hour. Determine a 95% confidence interval estimate for the speed of all cars.

A random sample of 144 observations has a mean of 20, a median of 21, and a mode of 22. The population standard deviation is known to equal 4.8. The 95.44% confidence interval for the population mean is

If an interval estimate is said to be constructed at the 90% confidence level, the confidence coefficient would be

Exhibit 8-5 A random sample of 64 SAT scores of students applying for merit scholarships showed an average of 1400 with a standard deviation of 240. -Refer to Exhibit 8-5. If we want to provide a 95% confidence interval for the SAT scores, the degrees of freedom for reading the critical values of "t" statistic is