## Polinomial regression

Hello, could you explaine to a newby when / in which cases does it apply polinomial (non linear) regressions?

I know that they generate a curve line which fits the datas. What I don’t understand is when is used this kind of regression.

In linear regression we have IV and DV and we want to extimate a correlation between, and the regression line which fits the data is the expression of this correlation and the Least squared computation which produce a linear rect, But how and WHEN do it originates a curvilinear line?

In which cases? Could you make an example? with an IV and a DP. V ?

submitted by Nevin Manimala Nevin Manimala /u/luchins

## How to handle “secondary control”

Hi! I could use some help on a experiment on plants.

The experimental design had three different types of treatments and one “normal control” and another control that was purely there to test if pH had an effect (the other treatments were of a nature that made some pH change inevitable). Let’s call it a pH control henceforth.

My question is if the pH control must be included in the ANOVA’s used to analyse the data or if it would be acceptable to first test if there’s difference between the two controls and if there isn’t then continue the analysis without the pH control. Is one option more correct than the other?

submitted by Nevin Manimala Nevin Manimala /u/SwoldierofBrodin

## Is there a nice way to tell drivers to gtfo the left lane

There are a lot of 2 lanes in one direction roads around where I live. Way too often I will be driving say 65 and no one else is on the road but two cars in front of me pacing each other at 60 for miles.

What’s the most polite way to get them to move over, I don’t want to be mean but most the time I don’t even think they realize what they are doing.

Flashing lights would seem like the best option. Riding them close? Passing on shoulder? (Gumball style)

submitted by Nevin Manimala Nevin Manimala /u/PwnCall

## Matching Units by set of Characteristics, without treatment/controls

Hi all,

I’m working with a data set of school characteristics ranging from student and teacher demographics to poverty rankings across years. This data set is slated to be used for matching similar schools as a control for future analysis of the impacts a treatment has on a class’ various outcomes.

My Question:

I understand matching is often done with knowledge of which units have been treated and which are controls, but is it possible/done to do a preemptive match by characteristics without such present knowledge of treatment status?

I can understand propensity matching and the like but can’t seem to find a way to implement this kind of matching via Stata.