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Chapter 8: Q 67. (page 542)
Blood pressure A medical study finds that and
for the seated systolic blood pressure of the randomly selected adults. What is the standard error of the mean? Interpret this value in context.
Mean standard error is
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Most people can roll their tongues, but many can鈥檛. The ability to roll the tongue is
genetically determined. Suppose we are interested in determining what proportion of students can roll their tongues. We test a simple random sample of students and find that can roll their tongues. The margin of error for a confidence interval for the true proportion of tongue rollers among students is closest to which of the following?
a.
b.
c.
d.
e.
Willows in Yellowstone Writers in some fields summarize data by giving x 虅 and its
standard error rather than .Biologists studying willow plants in Yellowstone National Park reported their results in a table with columns labeled The table entry for the heights of willow plants (in centimeters) in one region of the park was . The researchers measured a total of plants.
a. Find the sample standard deviation for these measurements.
b. A hasty reader believes that the interval given in the table is a confidence interval for the mean height of willow plants in this region of the park. Find the actual confidence level for the given interval.
Travel time to work A study of commuting times reports the travel times to work of a random sample of employed adults in New York State. The mean is minutes and the standard deviation is
minutes. What is the standard error of the mean? Interpret this value in context.
BlinkWhen two lights close together blink alternately, we 鈥渟ee鈥� one light moving back and forth if the time between blinks is short. What is the longest interval of time between blinks that preserves the illusion of motion? Ask subjects to turn a knob that slows the blinking until they 鈥渟ee鈥� two lights rather than one light moving. A report gives the results in the form 鈥渕ean plus or minus the standard error of the mean.鈥� Data for subjects are summarized as (in milliseconds).
a. Find the sample standard deviation for these measurements.
b. A hasty reader believes that the interval given in the report is a confidence interval for the population mean. Find the actual confidence level for the given interval.
Critical values What critical value from Table B should be used for a confidence interval for the population mean in each of the following situations?
a. A confidence interval based on randomly selected observations
b. A confidence interval from an SRS of observations
c. A confidence interval based on a random sample of size
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