Determining Sample Size . In Exercises 31–38, use the given data to find the minimum sample size required to estimate a population proportion or percentage. 32. Chickenpox You plan to conduct a survey to estimate the percentage of adults who have had chickenpox. Find the number of people who must be surveyed if you want to be 90% confident that the sample percentage is within two percentage points of the true percentage for the population of all adults. a. Assume that nothing is known about the prevalence of chickenpox. b. Assume that about 95% of adults have had chickenpox. c. Does the added knowledge in part (b) have much of an effect on the sample size?
Determining Sample Size . In Exercises 31–38, use the given data to find the minimum sample size required to estimate a population proportion or percentage. 32. Chickenpox You plan to conduct a survey to estimate the percentage of adults who have had chickenpox. Find the number of people who must be surveyed if you want to be 90% confident that the sample percentage is within two percentage points of the true percentage for the population of all adults. a. Assume that nothing is known about the prevalence of chickenpox. b. Assume that about 95% of adults have had chickenpox. c. Does the added knowledge in part (b) have much of an effect on the sample size?
Solution Summary: The author explains that the margin of error is 2% and the confidence level is 90%. The critical value is the average of the z-values 1.64 and 1.65.
Determining Sample Size. In Exercises 31–38, use the given data to find the minimum sample size required to estimate a population proportion or percentage.
32. Chickenpox You plan to conduct a survey to estimate the percentage of adults who have had chickenpox. Find the number of people who must be surveyed if you want to be 90% confident that the sample percentage is within two percentage points of the true percentage for the population of all adults.
a. Assume that nothing is known about the prevalence of chickenpox.
b. Assume that about 95% of adults have had chickenpox.
c. Does the added knowledge in part (b) have much of an effect on the sample size?
Features Features Normal distribution is characterized by two parameters, mean (µ) and standard deviation (σ). When graphed, the mean represents the center of the bell curve and the graph is perfectly symmetric about the center. The mean, median, and mode are all equal for a normal distribution. The standard deviation measures the data's spread from the center. The higher the standard deviation, the more the data is spread out and the flatter the bell curve looks. Variance is another commonly used measure of the spread of the distribution and is equal to the square of the standard deviation.
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