[17.9] the chi-squared test
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what is the chi-squared test used to test?
whether any deviation between the observed and expected numbers in an investigation is significant or not
what criteria are necessary to use a chi-squared test?
• relatively large sample size >20 • discrete data • only raw scores, not percentages etc. • used to compare experimental results with theoretical ones
what is the formula for chi²?
X² = Σ (observed value - expected value)² / (expected value)
how do you find the degrees of freedom?
number of categories - 1
when should you accept the null hypothesis based on the critical value table?
• calculated value is smaller than critical value • there is more than 5% probability that the differences between observed and expected values is due to chance • we accept the null hypothesis
when should you reject the null hypothesis based on the critical value table?
• calculated value is greater than critical value • there is less than 5% probability that the differences between observed and expected values is due to chance • we reject the null hypothesis