17.8 - Chi-squared Test Flashcards
How chi-squared tests can be used to analyse genetic crosses The key steps in the chi-squared test How to calculate the chi-squared statistic How to compare chi-squared values to critical values
What is the chi-squared (χ2) test?
Statistical tool to measure differences between observed and expected results
What are the criteria for using the χ2 test?
- Large sample size
- Discrete data categories (like yes or no, heads or tails, red or blue)
- Using raw counts (not percentages or rates)
- A comparison of experimental and theoretical results
What are the steps in the χ2 test?
Propose alternative and null hypotheses
What is the null hypothesis?
No significant difference between observed and expected results
What is the formula for the χ2 statistic?
χ2 = Σ[(O-E)^2 / E]
How do you calculate the χ2 statistic?
Calculate expected values
How do you compare the χ2 statistic to the critical value?
Choose probability level
What are degrees of freedom (df)?
Number of phenotypes - 1
What does it mean if the χ2 statistic is greater than or equal to the critical value?
Difference is significant
What does it mean if the χ2 statistic is less than the critical value?
Difference is likely due to chance
