Linear regression lesson should not depend on correlations

[schanzer]

In reading through the AI materials, I found myself in a familiar place: wanting kids to know linear regression but not caring if they know how to interpret correlations!

I am now more firmly convinced that the LR lesson could include a single paragraph that explains r, which would be a review for kids who completed correlations but introduce just enough information that a student could complete the LR lesson without ever doing correlations.

This would benefit both AI and Alg2, and requires minimal effort.

[retabak]

The linear regressions lesson already incorporates lots of review in the first section. Students make scatterplots, and think about r on both lr-plot-intro and drawing-predictors!