# Correlations and Regressions

- Created by: eleanor
- Created on: 11-04-15 14:15

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- Correlation and Regression
- Correlation
- for positive correlation the points on the scatter diagram increase as you go from left to right.
- for a negative correlation the point on the scatter diagram decrease as you from left to right.
- r is a measure of linear relationship
- r=1 perfect positive linear correlation
- r= -1 perfect negative correlation
- r=0 no linear correlation

- Coding
- you can rewrite the variable x and y using coding
- r is not affect by coding

- Regression
- the equation of the regression line of y on x
- y = a +bx
- where b =Sxy / Sxx
- a = ?y -b ?x

- Coding
- to turn a coded regression line in to an actual regression line substitute the codes into the answer

- the purpose of the regression line is to make predictions about values of one variable for some given values of the other
- predictions should only be made in the range of the data
- extrapolaion are predictions made outside the range of data and are unreliable

- outliers do effect the regression line

- the equation of the regression line of y on x

- Correlation

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