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Mathematics 12 Online
OpenStudy (anonymous):

What is the 90% confidence interval for the variance of exam scores for 28 algebra students, if the standard deviation of their last exam was 12.7?

OpenStudy (mathmale):

I assume you're familiar with "z-critical value." If so, please determine that for a 90% confidence interval. If you're unsure, try doing an Internet search for "z-critical value." What is n, the sample size? Is this a sampling of students, or is this the student population? What is the formula for confidence interval when the population standard deviation is unknown, but the sample s. d. is known?

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