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Chapter 8: Q.12 (page 477)
Suppose the Census needed to be confident of the population mean length of time. Would the Census have to survey more people? Why or why not?
It is not required for the census to survey a larger number of people because the level of confidence does not depend on the sample size.
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The mean age for all Foothill College students for a recent Fall term was . The population standard deviation has been pretty consistent at . Suppose that twenty-five Winter students were randomly selected. The mean age for the sample was . We are interested in the true mean age for Winter Foothill College students. Let the age of a Winter Foothill College student.
role="math" localid="1648389122287"
The data in Table 8.10 are the result of a random survey of 39 national flags (with replacement between picks) from various countries. We are interested in finding a confidence interval for the true mean number of colors on a national flag. Let X = the number of colors on a national flag.
Construct a 95% confidence interval for the true mean number of colors on national flags.
Using the same , , and n = 39, how would the error bound change if the confidence level were reduced to 90%? Why?
The standard deviation of the weights of elephants is known to be approximately pounds. We wish to construct a % confidence interval for the mean weight of newborn elephant calves. Fifty newborn elephants are weighed. The sample mean is 244 pounds . The simple standard deviation is 11 pounds.
1. Identify the following:
a. x- = _____
b. 蟽= _____
c. n= _____
The Ice Chalet offers dozens of different beginning iceskating classes. All of the class names are put into a bucket. The 5 P.M., Monday night, ages 8 to 12, beginning ice-skating class was picked. In that class were 64 girls and 16 boys. Suppose that we are interested in the true proportion of girls, ages 8 to 12, in all beginning ice-skating classes at the Ice Chalet. Assume that the children in the selected class are a random sample of the population.
State the estimated distribution of
Of 1,050 randomly selected adults, 360 identified themselves as manual laborers, 280 identified themselves as non-manual wage earners, 250 identified themselves as midlevel managers, and 160 identified themselves as executives. In the survey, 82% of manual laborers preferred trucks, 62% of non-manual wage earners preferred trucks, 54% of mid-level managers preferred trucks, and 26% of executives preferred trucks.
We are interested in finding the 95% confidence interval for the percent of executives who prefer trucks. Define random variables X and P鈥� in words.
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