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the crack length [in micrometers (µm)] of a randomly selected crack is normally distributed with an average length of 71 and a variance of 6.25. (a) What percantage of cracks are over 74 &micr
She randomly samples 67 CFOs and finds that 40 of them get their money news from newspapers. Does the test show enough evidence to reject the findings of Robert Half International? Use α = .0
If you had used the critical value method, what would the two critical values be? How do the sample results compare with the critical values?
A box contains four 40-W bulbs, five 60-W bulbs, and six 75-W bulbs. Suppose that three bulbs are randomly selected. What is the probability that exactly two of the selected bulbs are rated 75W?
In establishing a set of hypotheses which we are testing, we rely on the standard error. What two parameters are used to determine the standard error?
For each of the following α values, compute the probability of committing a Type II error if the population mean actually is 99.
What was the product being analyzed using just the amount of rain and average temperature to predict quality in the text Supercrunchers?
Suppose each of the numbers 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 is written on a separate poker chip and placed in a hat. If one of the chips is randomly selected, determine the probability that the c
In a city of 120,000 people there are 20,000 norwegians. What is the probability that a randomly selected person will be norwegian?
If a group of 4 were randomly selected from a group of 6 people (3 female;3 males) what is the probability the selected group will consist of 1 male and 3 females?
Suppose a researcher believes that the average annual earnings of a BMW driver are lower now, and he sets up a study in an attempt to prove his theory.
He randomly samples 18 BMW drivers and finds out that the average annual salary for this sample is $78 974, with a population standard deviation of $7810. Use α = .01 to test the researcher's
What is the probability of having the same number when rolling two dices? What is the probability of having at least 2 numbers the same when rolling three dices?
A sample of n 8 scores has a mean of M 12. One new score is added to the sample and the new mean is found to be M 13. What is the value of the new score?
A sample of n 4 scores has a mean of M 12. A second sample of n 6 scores has a mean of M 8. If the two samples are combined, what value will be obtained for the mean of the combined sample?
We have a carton of 12 rechargeable batteries contains two that are defective. In how many ways can the inspector choose 3 of the batteries and get
Calculate the confidence interval for the proportion of respondents who stated they are former smokers.
If 60 percent of those people chewing the gum are successful in stopping smoking, what is the probability that in a group of four smokers using the gum at least one quits smoking?
Twelve case of leukemia are reported in people living in a particular census tract over a 5 year period. Is the number of cases abnormal if only 6.7 cases would be expected based on national cancer-
In pharmacological research a variety of clinical chemistry measurements are routinely monitored closely for evidence of side effects of the medication under study. Suppose typical blood-glucose lev
A scientist attempts to perform a difficult experiment. She is successful in about 80% of her attempts. She attempts the experiment 6 times. Let X is the number of these attempts that succeed. Find
Use the normal approximation to the binomial to find the probability of X = 20 when n = 30 and p = 0.5.
The average charitable contribution deduction on federal tax returns for the year 2007 was $625. Suppose that the distribution of contributions is normal with a standard deviation of $100.
Consider the following frequency of demand: If the simulation begins with 0.8102, the simulated value for demand would be
An old study of 1000 people in Phoenix found that 27 were obese. Find the 99% confidence interval of the population proportion of persons living in Phoenix who are obese.