Outlier Detection and Power Analysis (t-test & ANOVA)

  1. Produce a histogram and a boxplot for the “years married prior to separation” (mar) variable.
    1. How many outliers are suggested by the histogram?
    2. How many outliers are suggested by the boxplot?
    3. Use the z-score method to identify outliers. Using the ID variable, please indicate which cases are identified as outliers using the z-score method?
    4. Run a independent samples t-test using gender as the predictor and years married prior to separation as the dependent variable.
      1. State the null and alternative hypotheses.
      2. Using one sentence, report the t-test results
  • Was the t-test significant? Interpret the results in light of the significance value.
  1. Did the t-test suggest small, medium, or large differences between gender of the individuals and years married prior to separation? (Hint: use G*Power to calculate Cohen’s d, and then use the rules of thumb in the lecture notes).
  2. Now, take out the outliers detected using the z-score method (i.e., delete them from the dataset). Now run the t-test again.  Was there any change in either the interpretation of the significance probability value or the effect

 What are the effects of marital status (excluding the widowed group) on life satisfaction?

  1. State the independent and dependent
  2. State the null and alternate
  3. Run the appropriate analysis using SPSS (Hint: Use the General Linear Models

and Univariate Procedure. Select Estimates of Effect Size under the Options tab).

  1. What are the mean and standard deviation for each of the levels of the IV?
  2. Report the appropriate F statistic, degrees of freedom, p value, and eta squared (η2).
  3. What is your decision regarding the null hypothesis (i.e., did you reject or fail to reject the null)? Explain your decision (1 sentence)
  4. What is the effect size for this analysis? (i.e., the eta squared).   Was the effect size small, medium, or large?
  5. Suppose you wanted to conduct a new study that includes marital status and life satisfaction. Based on a power analysis using G*Power, what is the minimum sample size required for running the study based on power of .80.

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