Inferences with Two Means: Independent Samples Access tech supplements, videos, and data sets at www.TriolaStats.com TECH CENTER continued R R command: t.test(x, y, alternative=c(“two.sided”, “less”, “greater”), paired=FALSE, conf.level=0.952 where x is a vector of group 1 sample data and y is a vector of group 2 sample data. TIP: For Example 1: t.test(x, y, alternative=“less”, paired=FALSE, conf.level=0.902 A complete list of R statistical commands is available at TriolaStats.com Excel Hypothesis Test XLSTAT Add-In Requires original sample data; does not work with summary data. 1. Click on the XLSTAT tab in the Ribbon and then click Parametric tests. 2. Select Two-sample t-test and z-test from the dropdown menu. 3. For Data format select One column per sample. Under Sample 1 & 2 enter the range of cells containing the sample data. 4. Select Student’s t test. 5. If the first row of data contains a label, check the Column labels box. 6. Click the Options tab. 7. Under Alternative hypothesis select the desired format (3 for two-tailed test, * for left-tailed test, + for right-tailed test). Enter 0 for Hypothesized difference (D) and enter the desired significance level (enter 5 for 0.05 significance level). Select Asymptotic p-value. 8. Uncheck the Assume equality box and uncheck the Cochran-Cox box. Uncheck the Use anF-test box. 9. Click OK to display the test statistic (labeled t Observed value) and P-value. Excel (Data Analysis Add-In) 1. Click on Data in the ribbon, then click on the Data Analysis tab. 2. Select t-Test: Two-Sample Assuming Unequal Variances and click OK. 3. Enter the data range for each variable in the Variable Range boxes. If the first row contains a label, check the Labels box. 4. Enter 0 for Hypothesized Mean Difference. 5. Enter the desired significance level in the Alpha box and click OK. The test statistic is labeled t Stat and P-value is labeled P. Confidence Interval XLSTAT Add-In (Required) Requires original sample data; does not work with summary data. 1-5. Follow above Steps 1–5 for Hypothesis Test using XLSTAT Add-In. 6. Click the Options tab. 7. Under Alternative hypothesis select the two-tailed option 3. Enter 0 for Hypothesized difference (D) and enter the desired significance level (enter 5 for 95% confidence level). Select Asymptotic p-value. 8. Uncheck the Assume equality box and uncheck the Cochran-Cox box. Uncheck the Use anF-test box. 9. Click OK to display the confidence interval. 9-2 Two Means: Independent Samples 463
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