Chi-Square

• Source used for example Qs (except the calculations)

  
• Example answer

  
• Formula to calculate Chi-square + to calculate expected frequencies

  
• Calculating Chi-Square step 1

  work out the row and column totals for each cell + the overall total

  
• Step 2

  use the formula to calculate the expected frequency for each cell

  
• Step 3 + 4

  use the formula to calculate the chi-square value

  then calculate degrees of freedom

  if observed value is greater than critical value, results = significant

  
• To read the critical values table for Chi-Square we need to know:

  -the level of significance (usually 0.05)

  -the degree of freedom
• How to calculate degrees of freedom

  df = (number of rows - 1) x (number of columns - 1)
• Example Q: How would you read a critical values table for this Chi-Square test (2)

  We read the critical value at the 0.05 level of significance and find the degrees of freedom (2) in order to find the critical value of 5.991

  
• Significant statement example:

  
• How to decide if the critical value needs to be smaller or larger for the results to be significant

  if the observed value is gReater than the critical value, look for an R for significance - speaRman's Rho and chi squaRe

  e.g in Chi-square if the observed value is bigger than the critical value, results are significant but in Mann Whitney if the observed value is bigger than the critical value, the results aren't significant