A researcher knows from the past that the standard deviation of the time it takes to...

A researcher knows from the past that the standard deviation of the time it takes to inspect a car is 16.8 minutes. A random sample of 24 cars is selected and inspected. The standard deviation is 12.5 minutes. At a= 0.05, can it be concluded that the standard deviation has changed? Use the P-value method. Assume the variable is normally distributed.

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orchestra answered 1 year ago

Colleen knows the population mean she is working with is 90 and the standard deviation of...

Colleen knows the population mean she is working with is 90 and the standard deviation of this population is 4. She predicts she will obtain a sample mean of 91 with a sample size of 16. She sets her alpha level to 0.01 and her research hypothesis is two-tailed. What is the power of her study? ans = 5.73%

EKU knows that on average 8.7 percent of students with a standard deviation of 3.0 will...

EKU knows that on average 8.7 percent of students with a standard deviation of 3.0 will fail an EKU course. The psychology department wanted to know if their summer courses had a similar number of failing students. Dr. Lawson looked at the failing rates for the most recent summer courses (9 courses) and got the following data. Use a single-sample z-test to determine the outcome (alpha = .05, two-tailed). Class 1: 11.0 % failed Class 2: 8.4 % failed Class...

A study takes a SRS from a population of full-term infants. The standard deviation of birth...

A study takes a SRS from a population of full-term infants. The standard deviation of birth weights in this population is 2 pounds. Calculate 95% confidence intervals for μ for samples in which: a) n = 81 and = 7.0 pounds b) n = 9 and = 7.0 pounds c) Which sample provides the most precise estimate of the mean birth weight? d) Interpret the CI you computed in part a).

An employee takes time of her trip from her home to office as normally distributed with a mean of 21 minutes and a standard deviation of 7 minutes.

An employee takes time of her trip from her home to office as normally distributed with a mean of 21 minutes and a standard deviation of 7 minutes. What proportion of her trip takes between 25 and 29 minutes? Draw the graph also. Find the probability that standard normal random variable takes on the given values. Show the required area on the graph. Pz=2.5 Pz0-Pz<-1.96 P-1.05<z P-∞<z<+ 2 P0<z<1

A researcher is interested in a possible relationship between height and the time it takes to...

A researcher is interested in a possible relationship between height and the time it takes to run a 100 meters. With a random sample of 57 people, the researcher finds a Pearson correlation coefficient r = − 0.492. Group of answer choices A. There is a very strong correlation between these variables. As height increases, generally the 100-meter run time decreases. B. There is a very strong correlation between these variables. As height increases, generally the 100-meter run time increases...

A researcher is interested in the mean amount of time it takes people to complete a...

A researcher is interested in the mean amount of time it takes people to complete a personality questionnaire. He selects 40 people at random and calculates the mean amount of time to be 20.4 min with a variance of 17.64 min2 . a) Define the parameter of interest. b) Define the random variable of interest. c) Name the distribution required to calculate confidence intervals. (Check the relevant criteria.) d) Construct a 98% confidence interval for the true mean amount of...

4. From past experience, the owner of a restaurant knows that, on average, 5% of the...

4. From past experience, the owner of a restaurant knows that, on average, 5% of the groups that make reservations never show, and 7% of the groups that make reservations show up late (the other 88% percent show up on time). a) How many reservations can the owner accept and still be at least 80% sure that all parties that make a reservation will show? b) How many reservations can the owner accept and still be at least 90% sure...

A researcher claims that New Zealanders spend more time exercising than Australians. The researcher takes a...

A researcher claims that New Zealanders spend more time exercising than Australians. The researcher takes a random sample of 41 New Zealanders and finds that they spend an average of 130 minutes per day exercising, with a standard deviation of 24. A sample of 61 Australians averaged 110 minutes a day of exercise, with a standard deviation of 16. Assuming equal variances, test the claim that New Zealanders exercise more than Australians at the 0.05 significance level. Assuming unequal variances,...

A book publisher knows that it takes an average of nine business days from when the...

A book publisher knows that it takes an average of nine business days from when the material for the book is finalized until the first edition is printed and ready to sell. Suppose the exact amount of time has a standard deviation of four days. Use an appropriate normal transformation to answer the following questions. a. Suppose the publisher examines the printing time for a sample of 36 books. What is the probability that the sample mean time is shorter...

A CPA knows from past history that the average accounts receivable for a company is $521.72...

A CPA knows from past history that the average accounts receivable for a company is $521.72 with a standard deviation of $584.64. If the auditor takes a simple random sample of 100 accounts, what is the probability that the mean of the sample is within $120 of the population mean?

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