STAB22H3 Lecture Notes - Lecture 2: Marginal Distribution, Confounding
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If the conditional distribution of one variable does not depend on the other variable (hence, each conditional distribution resembles the marginal distribution), these two variables are said to be independent. Example: gender and drinking are not independent, i. e. there might be a association between these variables. Each bar is divided into segments , such that the length of each segment indicates proportion or percentage of observations in a second variable. Conclusion: women will go more dancing than men. An association that holds for all of several groups can reverse direction when the data are combined to form a single group. We give each drug to a group of people and then count the number of successes (improvements) and failures (no change) for each group. Simpson"s paradox is named after edward simpson, who first described this paradox in the 1951 paper "the interpretation of interaction in contingency. Pearson and yule each observed a similar paradox half a century earlier than.
