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Chapter 2G Statistical Tools in Evaluation

Chapter 2G Statistical Tools in Evaluation. Hypothesis Testing. 1. Develop a research hypothesis of potential relationship. 2. Determine the statistical null hypothesis. 3. Determine the alternative hypothesis. 4. Obtain the data. 5. Make the decision based on probability (p-value).

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Chapter 2G Statistical Tools in Evaluation

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  1. Chapter 2GStatistical Tools in Evaluation

  2. Hypothesis Testing 1. Develop a research hypothesis of potential relationship. 2. Determine the statistical null hypothesis. 3. Determine the alternative hypothesis. 4. Obtain the data. 5. Make the decision based on probability (p-value).

  3. Normal Distribution

  4. The Null and Alternative Hypotheses

  5. Variable Classification Independent Presumed cause Manipulated Predicted to Predictor Dependent Presumed effect Measured Predicted from Criterion

  6. Differences Among Groups • Determine whether subjects mean scoresare different on some dependent variable. • Assumes homogeneity of variance. • Compare twoormoretests or groups. • Betweengroups and withinsubjects. • Inferfrom mean score of sub-group to population.

  7. Selected Statistical Tests Independent t-test for twobetween groups Dependent t-test for twowithin groups (test/re-test) One-way ANOVA for three or more between groups Repeated measures ANOVA for three or more within groups (test/re-test)

  8. What Analysis? Independent Dependent Statistical variable variable test 1 nominal (2 groups) 1 nominal independent t test 1 nominal (pre/post) 1 continuous dependent t test 1 nominal (>2 groups) 1 continuous One-way ANOVA 2 nominal (>2 groups) 1 continuous Repeated ANOVA

  9. Statistical Test Examples Independent t-test - differences in girls and boys Dependent t-test - pre and post measurement One-way ANOVA - more than 2 groups Repeated measures ANOVA - more than 2 tests-test/re-test

  10. Additional Statistics • t-Tests • used to compare two means. • is one mean significantly higher than another mean? • this is sometimes used to demonstrate known groups evidence of validity.

  11. t-Tests • t-test for two independent groups • t-test for two dependent groups

  12. t-Test Interpretation • If calculated |t-statistic| is  critical value from a table, reject null hypothesis; or • If p-value is ≤ .05 from computer printout, then reject null hypothesis. • If reject null hypothesis, the means are considered to be significantly different.

  13. t-Test for Two Independent Groups • Independent groups means the subjects in one group are not related to (independent of) the subjects in the other group. • t = (mean1 - mean2)  (SEmean1 + SEmean2) • SEmean1 = s1n1 SEmean2 = s2n2 • df = n1 + n2 - 2

  14. Sample SPSS Independent Groups t-Test

  15. t-Test for Two Dependent Groups • Dependent groups means the groups are correlated, paired, or matched in some fashion; or that you have the same subjects in both groups (e.g., pretest vs. posttest). • t = (mean1 - mean2) ÷ (SEmean1 + SEmean2 - 2(r)(SEmean1)(SEmean2) • df = n - 1

  16. Sample SPSS Dependent Groups t-Test

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