CH9: Testing the Difference Between Two Means, Two ...

CH9: Testing the Difference Between Two Means or Two Proportions Santorico - Page 343 CH9: Testing the Difference Between Two Means, Two Proportions, and Two Variances CH9: Testing the Difference Between Two Means or Two Proportions Santorico - Page 344 Section 9-1 Testing the Difference Between Two Means: Using the Z Test Suppose we are interested in determining if a certain medication relieves patients headaches. We give the drug/treatment to one group and give a placebo to a control group and compare the mean incidences of patient relief from the headache Between the two groups. If the treatment group had a statistically significant improvement in headache symptoms over the control group, then we can conclude the drug works. CH9: Testing the Difference Between Two Means or Two Proportions Santorico - Page 345 So our question might be, Is the mean incidence of headache relief different for the two groups?

the sample sizes of the groups are greater than 30. 3.The population standard deviation is (assumed) known. Formula: 1 2 /2 Note: When n 1 and n 2 are at least 30, then s 1 and s 2 ... Variances are assumed to be unequal: t (X 1 X 2) (P 1 P 2) s 1 2 n 1 s 2 2 n 2 where degrees of freedom is equal to the smaller of n 1 1 or n

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  Samples, Size, Unequal, Sample size

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