Population 1 mean1 standard deviation1 population 2

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Unformatted text preview: Class 14 McCombs Independent Samples We are interested in some quantity for each of the two populations. Population 1: mean=µ1 , standard deviation=σ1 , Population 2: mean=µ2 , standard deviation=σ2 . Take random samples n1 and n2 from each population to estimate the population mean difference µ1 − µ2 . Case I: Assume population standard deviations are equal, σ1 = σ2 Case II: Population standard deviations are not equal, σ1 ￿= σ2 Rafael Mendoza Elementary Business Statistics – Class 14 McCombs Independent Samples, Equal Population Standard Deviations Case Equal Population Std. Dev. σ1 = σ2 Confidence Interval for Difference Between Means: ¯ ¯ ¯ ¯ X1 − X2 ± t∗ × Standard Error for (X1 − X2 ) ¯ ¯ Standard Error: for (X1 − X2 ) = sp sp = ￿ ￿ 1 n1 + 1 n2 where (n1 − 1)s2 + (n2 − 1)s2 1 2 n1 + n2 − 2 Degrees of freedom: n1 + n2 − 2 Use StatTools to calculate the confidence interval Example: Treadmill Motors Rafael Mendoza Elementary Business Statistics – Class 14 McCombs Example: Treadm...
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