# Stats I Final Pitt 2

 Paired-sample t-test paired-sample t-test used to compare 2 means where subjects have been measured twice examples of when to use a paired-sample t-test paired-sample t-test - subject is measured twice on a DV pre and post treatment (aka pre-post design)subject is measured on a DV at different levels of an IV simultaneously (DV = SAT, IV = math, verbal)-subject can be more than one person (DV = happiness, IV = spouses (husband, wife)) Assumptions paired-sample t-test NormalityNo OutliersIndependence of subjects Assumptions: Normality paired-sample t-test the difference score of a DV (error term) should be normally distributedtested using Shapiro-Wilk Assumption: when Normality is violated paired-sample t-test a research question can still be answered by using an alternative test that does NOT assume normalitya non-parametric alternative to the paired-sample t-test is Wilcoxon signed rank test Assumption: Outliers paired-sample t-test has an undue influence on a statisticassumption is checked by examining histogram and Q-Q plot Assumption: Independence of Subjects paired-sample t-test design considerdationone subject score is not influenced by another subject in studycannot be tested using statistics Degrees of Freedom paired-sample t-test df= N-1 doesn't depend on the number of scores but rather on the number of subjects Confidence Interval paired-sample t-test interval estimationaccounts for uncertainty of error Disadvantages paired-sample t-test Order effect Carryover effects Test effects Disadvantages: Order effect paired-sample t-test when the outcome of the study is affected by the order in which the treatments were prepared. Two most common types: carryover and test effects Order effect: Carryover effects paired-sample t-test effects of one treatment do not end prior to the administration of another treatment, so the effects observed in the later treatment include residual effects of the former ex: testing new pill but not waiting long enough between dosages Order effect: Testing Effect paired-sample t-test fatigue and practice effects effects due to repeated testing of participants over time ex: taking the same test twice in a short period of time Counterbalancing paired-sample t-test common solution to an order effect the order of treatments is often counterbalanced so that some participants get treatment in order but other get a second order so that order effects can be assessed. Advantages paired-sample t-test Reduced error: variance within subjects is typically smaller than between subjects (smaller sampling error, more power) Number of subjects: paired-samples t-test requires smaller number of subjects to achieve the same power than the independent-samples t-test AuthorAnonymous ID187275 Card SetStats I Final Pitt 2 DescriptionStats I Final Pitt pt. 2 Updated2012-12-05T13:08:34Z Show Answers