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Chapter 7: Q. 1.2 (page 448)
The length of human pregnancies from conception to birth varies according to a distribution that is approximately Normal with mean days and standard deviation days.
What is the mean of the sampling distribution of ? Explain.
The mean is .
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Which one of the following would be a correct interpretation if you have a z-score of on an exam?
(a) It means that you missed two questions on the exam.
(b) It means that you got twice as many questions correct as the average student.
(c) It means that your grade was two points higher than the mean grade on this exam.
(d) It means that your grade was in the upper of all grades on this exam.
(e) It means that your grade is two standard deviations above the mean for this exam.
How tall? A random sample of female college students has a mean height of inches, which is greater than the -inch mean height of all adult American women.
A sample of teens A study of the health of teenagers plans to measure the blood cholesterol levels of an SRS of - to -year-olds. The researchers will report the mean from their sample as an estimate of the mean cholesterol level M in this population.
(a) Explain to someone who knows no statistics what it means to say that is an unbiased estimator of .
(b) The sample result x is an unbiased estimator of the population mean no matter what size SRS the study chooses. Explain to someone who knows no statistics why a large random sample gives more trustworthy results than a small random sample.
Sale of eggs that are contaminated with salmonella can cause food poisoning in consumers. A large egg producer takes an SRS of eggs from all the eggs shipped in one day. The laboratory reports thatof these eggs had salmonella contamination. Unknown to the producer, (one-tenth of 1%) of all eggs shipped had salmonella. Identify the population, the parameter, the sample, and the statistic.
A -question multiple-choice exam offers choices for each question. Jason just guesses the answers, so he has a probability of getting any one answer correct. You want to perform a simulation to determine the number of correct answers that Jason gets. One correct way to use a table of random digits to do this is the following:
(a) One digit from the random digit table simulates one answer, with 5right and all other digits wrong. Ten digits from the table simulate answers. (b) One digit from the random digit table simulates one answer, with 0 or 1 right and all other digits wrong. Ten digits from the table simulate answers.
(c) One digit from the random digit table simulates one answer, with odd right and even wrong. Ten digits from the table simulate answers.
(d) Two digits from the random digit table simulate one answer, with to right and to wrong. Ten pairs of digits from the table simulate answers.
(e) Two digits from the random digit table simulate one answer, with to right and to wrong. Ten pairs of digits from the table simulate answers.
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