statistical testing

• Inferential statistics 


  Use the data collected from the sample to make inferences about the behaviour of the entire target population.
• Inferential statistics table

  
• Sign test example


  This is a difference in self-report of 'feeling confident' or 'not confident' after 20 mins of intense exercise.
• Chi squared example


  There is a difference in choice of 'healthy' or 'unhealthy' food options in participants who read a positive climate news story and participants who read a negative climate news story.
• Wilcoxon example


  There is a reduction in 'cuteness' rating of baby photographs after watching a graphic video of childbirth.
• Mann Whitney example


  There is a difference in self-reported body image rating between teenagers assigned to the no social media group and teenagers assigned to the social media allowed group.
• Spearman's Rho example


  There is a correlation between the rating of life satisfaction (0-7) and family birth order.
• Related T test example


  Adrenaline levels (part per million/PPM) are lower in participants who walks a dog than matched participants who walk alone.
• Unrelated T-test example


  There is a difference in time taken (seconds) by university graduates and non-graduates to complete a sudoku.
• Pearsons R example


  There is a positive correlation between income ($ per year) and IQ score of a standardised test.
• Working out degrees of freedom


  For some of the statistical tests, such as chi-squared instead of N, degrees of freedom are used (df). It's likely that the degrees of freedom will be in the stem, however, you can be asked to calculate degrees of freedom using a formula.

  Degrees of freedom = (number of rows-1) x (number of columns-1)
• How to do a sign test

  Step 1: Subtract each participant's score in condition B from A. Clearly note the sign of each result (+ or -).

  Step 2: Work out the number of participants. Exclude any participants with the same score in both conditions.

  Step 3: Work out (s). This is the least frequent sign (+ or -).

  Step 4: Use the critical value table to find the critical value, read across from N calculated in step 3 and down from the level of significance required.

  Step 5: Compare the critical value to S. If S is equal to or less than the critical value the results are signicant.
• Related Design


  • Repeated measures
  • Matched pairs
• Unrelated design


  • Independent groups