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final cheat sheet

# final cheat sheet - -z-test and one-sample t-test These are...

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-z-test and one-sample t-test: These are used to compare one sample mean to a population mean or some other known value. -More common: compare two(or more) sample means to each other. -Two general research strategies: (1) Two completely separate (independent) samples. (2) Two related (dependent) samples. -chance (sampling error) Setting the Statistical hypothesis for Independent samples. Ho Ho: μ - μ = 0 or Ho: μ = μ H1 H : μ - μ ≠0 H : μ ≠ μ Independent Samples t Ratio Where 2 1 x x s - is the standard error of the mean difference Two Sample t-test Example Research Question: Does mental imagery change memory scores? State Statistical Hypothesis: Ho: μ rote = μ imagery H1: μ rote ≠ μ imagery Set Decision Criteria: -df= (n - 1) + (n -1) = w - If α=.05 and two-tailed test, from t-table, t(crit)= + or – 2.101 - Reject Ho if t(obtained) > t(crit) Compute test statistics (t (obtained)) Make Decision: Reject Ho -Mental imagery memory scores are significantly higher compared to rote scores, t(18) = -3.00 p< .05 Setting Decision Criteria for a Directional Test (one-tailed) -Mental imagery improves memory scores. H0: µ1> µ2 or H0: µ1-µ2> 0 H1: µ1<µ2 or H1: µ1-µ2<0 Where µ1=Rote Group and µ2=Imagery Group -In this case, set decision criteria: Critical region is in the lower tail of the distribution. df=(n1-1)+(n2-1)=(10-1)+(10-1)=18 If α=.05 and one-tailed test, from t-table, tcrit = - 1.734 Reject Ho if obtained falls within the critical region. Setting Decision Criteria for a Directional Test (one-tailed) -Mental imagery decreases memory scores. H0: µ1< µ2 or H0: µ1-µ2< 0 H1: µ1>µ2 or H1: µ1-µ2>0 -Where µ1=Rote Group and µ2=Imagery Group -In this case, set decision criteria: Critical region is in the upper tail of the distribution. Assumptions of the Independent Samples t-test -Independent Observations –Normality –Homogeneity of Variance Effect size. Small d=.2 Medium d=.5 Large d=.8 Dependent Samples t-test -The type of t-test you use is determined by the research design employed. (1) Use a one sample t-test if you wish to compare a single sample mean to a hypothesized population mean value. (2) Use a independent samples t-test if you have two independent sample means that you wish to compare. (3) Use a dependent samples t-test if you1) measure the same participants on a dependent variable at two different times , or 2) have two separate groups of participants that have been matched based on some characteristic. Dependent Sample t Ratio

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final cheat sheet - -z-test and one-sample t-test These are...

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