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Chapter 7: Q. 1.4 (page 448)
The length of human pregnancies from conception to birth varies according to a distribution that is approximately Normal with meandays and standard deviation days.
Find the probability that the mean pregnancy length for the women in the sample exceeds davs, Show your work.
The probability is
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Here is a dot plot of the adult literacy rates in countries in , according to the United Nations. For example, the lowest literacy rate was , in the African country of Burkina Faso. Use the dot plot below to answer Questions
Based on the shape of this distribution, what numerical measures would best describe it?
(a) The five-number summary
(b) The mean and standard deviation
(c) The mean and the quartiles
(d) The median and the standard deviation
(e) It is not possible to determine which numerical values to use.
Here is a dot-plot of the adult literacy rates in countries in, according to the United Nations. For example, the lowest literacy rate was , in the African country of Burkina Faso. Use the dot-plot below to answer the Question
The overall shape of this distribution is
(a) clearly skewed to the right.
(b) clearly skewed to the left.
(c) roughly symmetric.
(d) uniform.
(e) There is no clear shape.
T7.11. Below are histograms of the values taken by three sample statistics in several hundred samples from the same population. The true value of the population parameter is marked with an arrow on each histogram
Which statistic would provide the best estimate of the parameter? Justify your answer
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.
The number of undergraduates at Johns Hopkins University is approximately , while the number at Ohio State University is approximately . At both schools, a simple random sample of about of the undergraduates is taken. Each sample is used to estimate the proportion p of all students at that university who own an iPod. Suppose that, in fact, at both schools. Which of the following is the best conclusion?
(a) The estimate from Johns Hopkins has less sampling variability than that from Ohio State.
(b) The estimate from Johns Hopkins has more sampling variability than that from Ohio State.
(c) The two estimates have about the same amount of sampling variability.
(d) It is impossible to make any statement about the sampling variability of the two estimates since the students surveyed were different.
(e) None of the above
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