Term
Response variable: Categorical (2 groups) Explanatory variable: None 

Definition
ztest (onesample) testing a proportion assumptions  randomized collection of data, and proportion of success > 15 and proportion of failure > 15. 


Term
Response variable: Quantitative Explanatory variable: None 

Definition
ttest (onesample) testing a mean assumptions  randomized collection of data, approximately normal population distribution (only if n < 30). 


Term
Response variable: Categorical (2 groups) Explanatory variable: Categorical (2 groups) 

Definition
ztest testing two proportions assumptions  randomized collection of data, for ztest: proportion of success and failure in group 1 each are > 5, and proportion of success and failure in group 2 each are > 5. For CI: proportion of success and failure in group 1 each are > 10, and proportion of success and failure in group 2 each are > 10. For McNemar's test (dependent samples): b+c>30 (failure before and failure after). 


Term
Response variable: Quantitative Explanatory variable: Categorical (2 groups) 

Definition
ttest testing two means assumptions  independent, randomized collection of data, approximately normal distribution (if either first og second group has n < 30). 


Term
Response variable: Categorical (>2 groups) Explanatory variable: Categorical (>2 groups) 

Definition
ChiSquared test testing for dependence assumptions  randomized collection of data, expected count is >5 in all cells. 


Term
Response variable: Quantitative Explanatory variable: Categorical (>2 groups) 

Definition
ANOVA (analysis of variance) testing several means assumptions  normal distributions within each group, same standard deviation across all groups (works reasonably, if the SD is the same within a factor of two), independent samples, randomized collection of data. 


Term
Response variable: Quantitative Explanatory variable: Quantitative 

Definition
Linear regression assumptions  mean of y depends linearly on x, randomized collection of data, for each x the population values of y should follow a normal distribution with the same standard deviation for all x. Model checking: calculate standardized residuals (outliers?), histogram of standardized residuals (normal distribution), normal quantile plot of standardized residuals (normal distribution), scatterplot of residuals vs. x (linearity and constant standard deviation). 


Term
Response variable: Quantitative Explanatory variable: Categorical and/or quantitative 

Definition
Multiple regression assumptions  all y are normally distributed with the same standard deviation σ. µy = α + β1 x1 + β2x2 + · + βkxk. Calculate standardized residuals (outliers?) Histogram of standardized residuals (normal distribution) Normal quantile plot of standardized residuals (normal distribution) Scatterplot of residuals vs. each x (linearity and constant standard deviation) Scatterplot of residuals vs. predicted values (linearity and constant standard deviation) 

