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A random sample of 46 observations was selected from a normally distributed population. The sample mean was xbar=81, and the sample variance was s2=35.0. Does the sample show sufficient reason to conc
Select a variable that will enable you to compare proportions of two groups. Use sample sizes of at least 30. Use the z test for proportions to analyze the data.
If you wanted to determine which of the two learning programs made the bigger difference in the participant's knowledge and skills, what statistical tests would you perform? What assumptions would the
Suppose that the quarterly sales levels among health care information systems companies are approximately normally distributed with a mean of million dollars and a standard deviation of million dollar
200 students took a test. The scores were normally distributed. Your score was in the 60th percentile. How many people scored at or below your score?
The same survey was mailed to 500 adults aged 25–34 without the gift certificate. There were 65 responses from the first group and 45 from the second group. (a) Perform a two-tailed test compari
Two manufacturing facilities produce 1280 × 1024 LED (light-emitting diode) displays. Twelve displays are chosen at random from each lab, and the number of bad pixels is noted for each display.
From her firm’s computer telephone log, an executive found that the mean length of 64 telephone calls during July was 4.48 minutes with a standard deviation of 5.87 minutes.
Below are fertility rates (average children born per woman) in 15 EU nations for 2 years. (a) Make a scatter plot. (b) Find the correlation coefficient and interpret it.
A recent survey of 50 executives who were laid off from their previous position revealed it took a mean of 26 weeks for them to find another position.
A state meat inspector in Iowa has been given the assignment of estimating the mean net weight of packages of ground chuck labeled “3 pounds.” Of course, he realizes that the weights canno
As a condition of employment, Fashion Industries applicants must pass a drug test. Of the last 220 applicants 14 failed the test. Develop a 99 percent confidence interval for the proportion of applica
Braking distances of cars. A random sample of 13 four-cylinder cars is obtained and braking distances are measured and found to have a mean of 137.5 ft. and a standard deviation of 5.8 ft.
Sat verbal scores are normally distributed with a mean of 426 and a standard deviation of 94. Use the Empirical Rule to determine what percent of the scores lie between 332 and 426.
Using the full 5-step process test to see if a population mean is not 25. Sample data is: Mean 24, standard deviation 10 and a sample of 400 was taken.
A statistician was setting up a hypothesis test with a level of significance dictated by upper management. However, she was concerned that the test would return unacceptable type II errors. Which od t
Suppose that the census indicates the average American earns $36,345.45 per year. You are interested in the whether people who majored in political science earn an amount that is different than the av
What are the underlying assumptions of Spearman rank-order scale?
A psychologist is studying the distribution of IQ scores of girls at an alternative high school. In wishing to estimate the average IQ scores in this school.
The grades on a statistics midterm test are normally distributed with a mean of 78 and a standard deviation of 6
A manufacturer can typically process 176-264 devices a given period of concern. In this situation the processing event is either pass or fail.
Assume that the distribution is normal. Based on the Empirical Rule, how many students scored between 69 and 89?
Assuming everyone I ask says East, how does the probability change with the sample size? In other words, how is the probability different if 50 out 50 women say East instead of 5 out of 5 women?
Shaver Manufacturing, Inc., offers dental insurance to its employees. A recent study by the human resource director shows the annual cost per employee per year followed the normal probability distribu
In a school how is ztest used in time table ... one group that studies 7 periods a day of 45 mins each class and the other group can choose semester wise classes and their time period is 90 mins