Test at 5% level of the significance of the deviation. What we need to understand is that the related-samples t-test is performed by conducting a one-sample t-test on the difference scores. ... Lecture6_HypothesisTesting_ANOVA.ppt Author: Joshua Akey Created Date: The difference between the two sample means is compared to the expected difference between two population means When is unknown and when the data are of at least interval or ratio scale Assumes the two samples have equal variance (the ratio of the largest to the smallest should not exceed 4 to 1) INDEPENDENT GROUPS t- Test Chapter 9 Small sample test(t-test) Two sample t-test Compare two unpaired groups Paired t-test Wilcoxon Test McNemar’s Test Compare two paired groups Wilcoxon Test Binomial Test One sample t-test Compare one group to a hypothetical value. For this a sample of 14 rods was tested . Specify your null distribution: F and M have similar standard deviations/variances, so make a “pooled” estimate of variance. The t formula 95% CI using t-test Mean= 20 Sy = 5 N= 20 T-Tests Independent Samples T-Tests of Independence Used to test whether there is a significant difference between the means of two samples. What kind of sample size do we need for power of .8? The Homogeneity of Variance Assumption (cont.) Define your hypotheses (null, alternative) H0: ♂-♀ math SAT = 0 Ha: ♂-♀ math SAT ≠ 0 [two-sided] Two-sample t-test 2. 9-4. Chapter 11: The t Test for Two Related Samples 1 Repeated-Measures Designs • The related-samples hypothesis test Data Summary Two-sample t-test 1. The rejection regions for three posssible alternative hypotheses using our example data are shown below. ; plot x= power min = .5 max=.95; run; Two-sample t Test for 1 Computed N Total Mean Actual N Index Diff Power Total 1 0.3 0.801 352 2 0.4 0.804 200 3 0.5 0.801 128 4 0.6 0.804 90 Typical studies are underpowered. Can result in more powerful test than independent samples t-test. We are testing for independence, meaning the two samples are related or not. 21 Dependent Samples t Formulas 1. Two Sample t-test 28 - Module 28 Sample Size Determination 1. The mean & standard deviation obtained were 17.85 and 1.955 respectively. Two Sample t-test The General Situation An important issue in planning a new study is the determination of an appropriate sample size required to … 9-4 9-5; 13. A correlated (or paired) t test is concerned with the difference between the average scores of a single sample of individuals who is assessed at two different times (such as before treatment and after treatment) or on two different measures. I have also created a PowerPoint presentation that demonstrates how to use the Excel spreadsheet. If we were to perform an upper, one-tailed test, the critical value would be t 1-α,ν = 1.6495. For our two-tailed t-test, the critical value is t 1-α/2,ν = 1.9673, where α = 0.05 and ν = 326. • The assumption requires that the two populations from which the samples are obtained have equal variances. One-sample t-test and Paired t-test 2. Two-Sample T-Test Introduction This procedure provides several reports for the comparison of two continuous-data distributions, including confidence intervals for the difference in means, two-sample t-tests, the z-test, the randomization test, the Mann-Whitney U (or Wilcoxon Rank- Sum) nonparametric test, and the Kolmogorov-Smirnov test. 12 Hypothesis Testing for Two Sample Means The t-test. One-sample t-test and Paired t-test 2. Used when we have dependent samples matched, paired or tied somehow ; Repeated measures ; Brother sister, husband wife ; Left hand, right hand, etc. learn how to do the related samples t-test. Useful to control individual differences. 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