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The null hypothesis H 02 is that the mean difference (x1-x2) >= 0.8.The null hypothesis H 01 is that the mean difference (x1-x2) 0.8.So, we can eliminate one of the tests.ĭefine the two null and alternate Hypotheses for equivalence: Now here's where it gets interesting.because the one-tailed p-values are both less than 0.05. If both p-values are less than 0.05, the means are equivalent. Two-Sample Assuming Unequal Variances An independent t-test used to analyse data from two unrelated groups when the variance of the data within the. The Equivalence test will perform the calculations and interpret the results for you. Youll want to click on t-test: Two-Sample Assuming Unequal Variances. QI Macros will prompt for a significance level (default = 0.05 or 0.95):Īlong with the hypothesized mean difference ( Note: this difference will set the range acceptable for equivalence): I was recently explaining the WelshSatterthwaite equation's application to two sample t-tests of differing variances, but while going through an example using Excel's built in t-test function (type 3 for unequal variance) I for the life of me couldn't get my calculation to match up exactly with Excel's built-in t-test function. If not, read my guide on performing a t-test in Excel - its easier than you may. In StatTools, I'm selecting a confidence interval or hypothesis test about the difference in means of two independent samples. Welch t-test is just an adaptation of t-test, and it is used when the two samples have possibly unequal variances. Therefore, Welch t-test is performed by default. 'Equal Variances' and 'Unequal Variances' in Two-Sample Inferences. By default, the R t.test() function makes the assumption that the variances of the two groups of samples, being compared, are different. The data are from 72 young female anorexia patients. Let us look at a data set on weight change (anorexia), also from the MASS library. The paired t-test has the same assumptions of independence and normality as a one-sample t-test. Select the data within your Excel spreadsheet, click on QI Macros menu, Statistical Tools and select Equivalence test. Home Techniques and Tips StatTools 'Equal Variances' and 'Unequal Variances' in Two-Sample Inferences. Paired tests are used when there are two measurements on the same experimental unit.
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If they are, one measurement can be eliminated, saving time and money. Are the measurements equivalent at these two different points in time. Note: Excel does not do equivalence tests QI Macros adds this functionality.Īdhesive tape is measured immediately after production and 24 hours later.