Chi Squared Test

• What is the purpose of the chi-squared test?

  To determine significant differences in results
• What does a statistically significant difference suggest?

  Presence of an unaccounted factor
• What happens when the difference is not significant?

  Differences are due to chance alone
• When is the chi-squared test used?

  When data is categorical
• What are the steps to calculate chi-squared values?

  1. Obtain expected (E) and observed (O) results
  2. Calculate the difference between results
  3. Square each difference
  4. Divide each squared difference by expected value
  5. Sum the results to obtain chi-squared value
• What is the significance of the critical value in chi-squared tests?

  It helps interpret the chi-squared value
• What probability level do biologists generally use?

  0.05 or 5%
• What does a probability level of 0.05 indicate?

  5% chance results are due to chance

  
• How is the degrees of freedom calculated?

  Number of classes - 1
• If there are 2 phenotypes, how many degrees of freedom are there?

  1 degree of freedom
• What conclusion can be drawn if the chi-squared value is greater than the critical value?

  There is a significant difference
• What does it mean if the chi-squared value is smaller than the critical value?

  No significant difference exists
• What can be assessed using the critical values table?

  Probability level of significant differences

  
• What does a chi-squared value smaller than the critical value at 0.05 indicate?

  Probability of chance is between 5-10%
• What does a chi-squared value larger than the critical value at 0.001 indicate?

  Less than 0.1% chance of results being due to chance
• What is the expected ratio of phenotypes in a dihybrid cross?

  • Expected ratio: 9:3:3:1
  • Based on inheritance of two genes

  
• How do you calculate expected values from the total number of rabbits?

  Divide total by sum of ratio parts
• What conclusion is drawn from the chi-squared value of 0.56 compared to 7.82?

  No significant difference exists
• What does a chi-squared value of 0.56 indicate about the probability of chance?

  Higher than 10% probability of chance
• What should you do when calculating a chi-squared value?

  • Create a table for calculations
  • Helps avoid confusion
  • Ensures accuracy in results

  
• Why might results be significantly different in a chi-squared test?

  Linkage between the genes being analyzed