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Unformatted text preview: Confidence intervals: scenarios and data 1. σ known A candle making process is known to produce candles whose life times have a variance of 0.4 hours. However, the average lifetime is un known. The lifetimes of a random sample of six candles turned out to be 8.1, 8.7,9.2,7.8,8.4,9.4 hours respectively. Find a 99% confidence interval for the population mean. 2. σ unknown, n small, nonNormal An experiment was performed to de termine whether two different forms of iron (Fe 2+ and Fe 3+ ) are retained dif ferently in the body. If one form were retained better, it would be the better dietary supplement. The investigators divided 36 mice randomly into two groups of 18 each; one group was given Fe 2+ and the other Fe 3+ at the same concentration. The iron was administered orally; it was radioactively labelled so that a radiation counter could measure the amount administered and the amount retained after a fixed amount of time had elapsed. The percentage of iron retained is listed for each mouse below. Obtain a 95% confidence intervaliron retained is listed for each mouse below....
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 Spring '10
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