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Do students at various universities differ in how sociable they are? Twenty-five students were randomly selected from each of three universities in a region and were asked to report on the amount of
old showed a standard deviation of $170. What is the test statistic for testing the difference between these population variances at alpha =.01?
A recent national survey found that high school students watch an average of 6.4 videos per month. A random sample of 25 college students revealed that the mean number of videos watched last month w
Science scores for high school seniors in the United States are normally distributed with a mean of 65 and a standard deviation of 18. Students scoring in the top 3% are eligible for a special prize
Over the past few weeks, we have studied a number of different hypothesis tests including the following:
The time needed to complete a final examination in a particular college course is normally distributed with a mean of 77 minutes and a standard deviation of 12 minutes. Answer the following questio
construct the 95% confidence interval for the percentage of all boards in this shipment that fall outside the specifications.
The daily rainfall experienced by Soaking City has been recorded on 10 randomly selected days throughout the year. This process has been repeated for every possible combination of 10 days in a year.
The members at or below the 20%ile of number of training days must attend a counseling session with one of the trainers. You will not have to attend such session if you have more than ______ trainin
A baseball player has a batting average of 0.325 each week of the season, with a standard deviation of 0.065. What is the z score when he bats 0.410 one week?
Given that the mean of a set of data is 25 and the standard deviation is 3, what is the coefficient of variation?
How often does the university admit a student with an SAT score of X=770 or above?
A brief description of the variable and whether the scale of measurement is nominal, ordinal, interval, or ratio, and why. Explain what it means to say that this variable is "normally distributed."
Suppose that 10 Cobalts are randomly selected and the miles per gallon for each are recorded. What is the probability that the mean miles per gallon exceed 34 miles per gallon?
Does lovastatin (a cholesterol-lowering drug) reduce the risk of heart attack? In a Texas study, researchers gave lovastatin to 2,325 people and an inactive substitute to 2,081 people (average age 5
A 90% confidence interval for the average number of children per household based on a simple random sample is found to be (0.7, 2.1). Can we conclude that 90% of households have between 0.7 and 2.1
The average number of mosquitos in a stagnant pond is 60 per square meter with a standard deviation of 12. If 16 square meters are chosen at random for a mosquito count, find the probability that th
Develop an interval estimate for the difference between the average yearly incomes of the marketing managers in the East and West. Use α = 0.05.
A sample has a mean of 115 and a standard deviation of 22. According to Chebyshev's theorem at least 75% of th data will fall between what values?
Use a 1% level of significance to test the claim that the distribution of first nonzero digits in the account file does not follow Benford's Law. (In other words, is there an indication of accountin
A quality engineer has collected data that reveals a machine takes an average of 10 minutes to complete a task with a standard deviation of 1.5 minutes. The engineer would like to know the probabili
27 of 8,500 people vaccinated against a certain disease later developed the disease. 38 of 10,000 people vaccinated with a placebo later developed the disease. Test the claim that the vaccine is eff
A manufacturing process produces items whose weights are normally distributed. It is known that 22.57% of all the items produced weigh between 100 grams up to the mean and 49.18% weigh from the mean
A sample of size n = 16 is used to perform a significance test for Ho: μ = 0 versus Ha: μ ≠ 0. The test statistic is t = 1.34. What are the right-tail probabilities p for these two entries?