Lecture 7 Chi-square Flashcards
(16 cards)
What type of data does the Chi-Square test analyze?
Categorical data.
What are examples of categorical data types?
Binary, Nominal, Ordinal.
What is the first step in calculating Chi-Square?
Cross-tabulate the variables to obtain observed frequencies.
What is the formula to calculate expected frequencies in Chi-Square?
E_ij = (row total_i × column total_j) / n
What is the formula for the Chi-Square statistic?
χ² = Σ[(Observed - Expected)² / Expected]
What does a Chi-Square test of independence assess?
Whether there is a significant association between two categorical variables.
What are residuals in a Chi-Square test?
The differences between observed and expected values in each cell.
What are standardised residuals?
Z = (O - E) / √E, where O is observed and E is expected frequency.
How do you calculate degrees of freedom (df) in a contingency table?
df = (number of rows - 1) × (number of columns - 1)
What does this result mean: χ²(6, n = 150) = 21.77, p < .01?
There is a statistically significant association between the variables.
How should expected counts be reported in a lab report?
Expected counts are used in calculation but not shown in the Results section.
How should observed counts be presented?
As a contingency table in the descriptive statistics section.
What do you include in the inferential statistics report?
Chi-square value, degrees of freedom, sample size, and p-value.
What should you avoid when writing about Chi-Square results?
Avoid repeating numbers, referring to the hypothesis, or duplicating info.
What does a significant standardised residual indicate?
That a specific cell differs more than expected by chance.
What is the key takeaway of a Chi-Square analysis?
It shows whether two categorical variables are statistically associated.
