March 2019
Beginner to intermediate
448 pages
13h 14m
English
In a linear model, the correlation between the features increases the variance for the associated parameters (the parameters related to those variables). The more correlation we have, the worse it is. The situation is even worse when we have almost perfect correlation between a subset of variables: in that case, the algorithm that we use to fit linear models doesn't even work. The intuition is the following: if we want to model the impact of a discount (yes-no) and the weather (rain–not rain) on the ice cream sales for a restaurant, and we only have promotions on every rainy day, we would have the following design matrix (where Promotion=1 is yes and Weather=1 is rain):
| Promotion | Weather |
| 1 |
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