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Unformatted text preview: Pvalue was less than the α value, we can conclude that the results are statistically significant and thus we can reject H o and assume H a . We have sufficient evidence to conclude that the mean diameter is significantly greater than 8.20mm. b) State: What is a 95% confidence interval estimate for the true mean diameter of the metal rods from this machine? Formulate: Observational study. Calculate a one sample t confidence interval for the true mean. The parameter is the true mean rod diameter, and the population is all metal rods from that machine. Use a level of confidence of 95%. Solve: See above for data plot and condition checks. (xbar) = 8.234mm. s = .025298mm. df = n–1 = 15–1 = 14 t confidence interval: (xbar) ± t * s / ( n^½) = 8.234 ± 2.145(.025298/[15^½]) = 8.234 ± 0.014 = (8.220, 8.248) Conclude: We are 95% confident that the true mean diameter of the metal rods produced by this machine is somewhere between 8.220mm and 8.248mm....
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 Winter '08
 Collings
 Statistics, Normal Distribution, mean rod diameter

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