A magazine includes a report on the energy costs per year for 32-inch liquid cry

Question

A magazine includes a report on the energy costs per year for 32-inch liquid crystal display (LCD) televisions. The article states that 14 randomly selected 32-inch LCD televisions have a sample standard deviation of $3.74. Assume the sample is taken from a normally distributed population. Construct 90% confidence intervals for (a) the population variance sigma^2 and (b) the population standard deviation sigma. Interpret the results. The confidence interval for the population variance is. (Round to two decimal places as needed.)

Explanation / Answer

alpha / 2 = 0.05 df = 13 X^2 = 22.362

1 - alpha/2 = 0.95 df=13 X^2 = 5.892

interval will be

13 * 3.74^2 / 22.362 < sigma2 < 13*3.74^2 / 5.892

8.13 < sigma^2 < 30.86

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