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Stats Class Question Im stuck on

A random sample of stock prices per share (in dollars) is shown. Find the 90% confidence interval for the variance and standard deviation for the prices. Assume the variable is normally distributed. Round the sample variance and final answers to three decimal places. 45.12, 10.87, 75.37, 28.37, 3.81, 26.69, 28.25, 43.00, 6.94, 46.12
________< σ2<__________
________< σ <__________
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1 Answer

Z for 90% is a range between -1.65 sigma to 1.645 sigma. So use your calculator or excel to find the variance, take the square root for sigma. And then multiply 1.645^2 by the variance for the range of positive and negative variance. multiply the sigma by 1.645 to get the range of positive and negative sigma.
Hope that helps!