1 / 15

Dependent t-Test

Dependent t-Test. CJ 526 Statistical Analysis in Criminal Justice. When to Use a Dependent t-Test. Two Dependent (related) Samples Repeated-Measures Design (before-after) Matched-Subjects Design. Example of a Dependent t-Test.

redford
Download Presentation

Dependent t-Test

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Dependent t-Test CJ 526 Statistical Analysis in Criminal Justice

  2. When to Use a Dependent t-Test • Two Dependent (related) Samples • Repeated-Measures Design (before-after) • Matched-Subjects Design

  3. Example of a Dependent t-Test • A forensic psychologist wants to determine whether physical exercise in a boot camp program has an effect on muscular strength. He/she measures the number of pull-ups 25 program participants complete at the beginning of the program (M = 3.28, SD = 1.88) and at the end of the program (M = 3.6, SD = 1.73).

  4. Example of a Dependent t-Test -- continued • Number of Samples: 2 (before & after) • Nature of Samples: dependent (same subjects at two different points in time)

  5. Example of a Dependent t-Test -- continued 3. Independent Variable: participation in boot camp--exercise 4. Dependent Variable and its Level of Measurement: number of pull-ups (ratio) 5. Target Population: boot camp participants

  6. Example of a Dependent t-Test -- continued 6. Appropriate Inferential Statistical Technique: t test, related samples • Null Hypothesis: no difference between the groups before and after boot camp exercise • Alternative Hypothesis: there will be a difference, boot camp participants will be able to do more pull ups after training • Decision Rule: • If the p-value of the obtained test statistic is less than .05, reject the null hypothesis, one-tail test

  7. Example of a Dependent t-Test -- continued 10. Obtained Test Statistic: t • Decision: accept or reject null hypothesis • D.f. = n-1 (in this case n – 1 = 25 – 1 = 24

  8. Results Section • The results of the Dependent t-Test involving participating in a physical exercise program as the independent variable and number of pull-ups as the dependent variable were not statistically significant.

  9. Discussion Section • It appears that participating in a physical exercise program did not have an effect on developing muscular strength among participants in a boot camp program.

  10. SPSS Paired-Samples t-Test Procedure • Analyze, Compare Means, Paired-Samples t-Test • Move pair of variables over to Paired Variables

  11. SPSS Paired-Samples t-Test Sample Printout

  12. SPSS Paired-Samples t-Test Printout • Paired Sample Statistics • Paired variables • Mean • N • Standard Deviation • Standard Error of the Mean

  13. SPSS Paired-Samples t-Test Printout -- continued • Paired Samples Correlations • Paired variables • N • Correlation • Sig • p-value of correlation coefficient

  14. SPSS Paired-Samples t-Test Printout -- continued • Paired Samples Test • Paired variables • Paired Differences • Mean of the Difference • Standard Deviation of the Difference • Standard Error of the Mean of the Difference • 95% Confidence Interval of the Difference • Lower • Upper

  15. SPSS Paired-Samples t-Test Printout -- continued • t: obtained test statistic • df: degrees of freedom • Sig: p-value • Divide by 2 to get one-tailed p-value

More Related