21) The Information Commons in the main library has 150 personal computers. The probability that any one of them will require repair on a given day is 0.02. To find the probability that exactly 25 of the computers will require repair, one would use what type of probability distribution?
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22) The local police department must write, on average, 5 tickets a day to keep department revenues at budgeted levels. Suppose the number of tickets written per day follows a Poisson distribution with a mean of 5.5 tickets per day. Interpret the value of the mean.
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23) Which of the following is a characteristic of every binomial distribution?
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24) The Big Red Arcade and Pizza Palace caters to young teens and sells tokens to play arcade games for 25¢ each and slices of pizza for 50¢ each. The following table details the distribution of sales of pizza slices per customer and sales of arcade tokens per customer.
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|
| # Slices of Pizza |
0 |
1 |
2 |
3 |
4 |
5 |
| Probability |
0.05 |
0.10 |
0.20 |
0.30 |
0.15 |
0.20 |
|
|
|
|
| # Arcade Games |
0 |
1 |
2 |
3 |
4 |
5 |
| Probability |
0.01 |
0.04 |
0.15 |
0.20 |
0.25 |
0.35 |
|
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What is the total expected per-customer revenue for pizza slice sales and arcade token sales?
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25) A popular restaurant recently asked 300 customers how may times per month they ate steak for dinner. The results were used to build the following probability distribution:
|
|
| x |
0 |
1 |
2 |
3 |
4 or more |
| P(x) |
0.05 |
0.10 |
0.20 |
0.30 |
0.15 |
|
|
The probability that a customer eats steak for dinner less than 3 times a month is
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26) Trudy Jones recently completed her certification examination and learned that her z-score was –2.5. The examining board also informed her that a failure to pass would be all scores that were 1 or more standard deviations below the mean and that those with scores higher than 2 standard deviations above the mean would receive a special commendation award. Trudy can, therefore, conclude that she
27) The expected value of the sampling distribution of the sample mean equals the population mean
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28) The use of the student’s t distribution requires which of the following assumptions?
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29) A random variable follows the student’s t distribution. The probability that it will be positive is
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30) A study of 200 insomniacs paid for by the Serta Mattress Company found that the average insomniac counted 350 sheep before falling asleep, with a standard deviation of 120. An insomniac is a person who has difficulty falling asleep. Some useful numbers might be:
|
|
| =NORMSINV(0.89) |
1.2265 |
| =NORMSINV(0.945) |
1.5982 |
| =TINV(0.89,199) |
0.1385 |
| =TINV(0.11,199) |
1.6053 |
| =TINV(0.055,199) |
1.9302 |
|
|
Calculate an 89% confidence interval for the true mean number of sheep counted by insomniacs.
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31) Ceteris paribus, which is narrower, a 95% confidence interval with n=100 or a 99% confidence interval with n=30?
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32) A random sample of 25 observations is selected from a normally distributed population. The sample variance is 10. In the 95% confidence interval for the population variance, the upper limit will be
33) When no point lies outside the control limits of a chart, we conclude that variation in the process is
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34) When a change has occurred in the mean of the process distribution, the result is referred to as
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35) In statistical process control, a Type I error occurs if we decide that the process is
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