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Ch.10: Sampling Distributions: ProportionWorksheetSee all chapters

# Sample Size

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Sections
Sampling Distribution for a Sample Proportion
Confidence Interval for a Population Proportion
Sample Size

Concept #1: Calculating the Minimum Sample Size Needed

Concept #2: Calculating the Minimum Sample Size Needed: Intro

Practice: A previous study found that your school consists of 60% White/Caucasian students. You want the 98% confidence interval for the proportion of White/Caucasian students to be no more than .05 away from the true proportion. How many students must you sample to create this confidence interval?

Practice: Rain in Florida is heavy during the spring. Assume that the standard deviation of average daily rainfall for the Spring is 8 inches. If you want to construct a 90% confidence interval to be within 2 inches of the true average rainfall in Florida, how many days need to be sampled?

Practice: It's said that most people prefer the color red. Your company has asked you to estimate the percent of people who prefer the color for manufacturing purposes. Construct a 95% confidence interval, but the company wants you to be within .01 of the population proportion.

Practice: You think you have a lot of speeding tickets so you decide to construct a 97% confidence interval for the average number of speeding tickets people your age receive. Assuming that the standard deviation is 10 tickets and that you want to be no more than 1 ticket away from the true average, how many random people do you need to sample?