What is a proportion in categorical data?
The number with a characteristic divided by the total number of individuals (p = x/n).
Which distribution describes probability for proportions?
The binomial distribution, which approximates a normal distribution for large n.
What is the formula for the standard error of a proportion?
√p(1−p) /n
What is a 95% confidence interval for a proportion?
p±1.96×SE
What does a contingency table do?
Summarizes data for two or more categorical variables and forms the basis for Chi-squared testing.
How is the expected frequency (E) in a contingency table calculated?
E = rowtotal x (columntotal/grandtotal)
When should you use a Chi-squared test vs Fisher’s exact test?
Chi-squared: large samples (expected ≥5). Fisher’s: small samples (expected <5).
What is the difference between odds and risk?
Odds: outcome vs alternative. Risk: outcome vs all outcomes.
What does an odds ratio represent?
How much more or less likely an outcome is in one group compared to another.
What does correlation measure?
The degree of association between two paired variables.
What is the Pearson correlation coefficient (r)?
Measures how close data points lie to a straight line (strength of linear relationship).
When should you use Spearman’s rank correlation instead of Pearson’s?
When data are not normally distributed or the relationship is not linear.
