Linear Regression Flashcards

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1
Q

When to use linear Regression?

A

If knowing the correlation isn´t enough. We want to find out more about the relation.

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2
Q

How to calculate linear regression using least square method?

A
  1. Calculate mean of x and y. This is the point where the linear regression line has to get through. p.e. (3/4)
  2. Take the simple linear regression equation
    ŷ = b0 + b1*x to calculate the slope (b1). The formula is Sum(x-xmean)(y-ymean) / Sum(x-xmean)**2
  3. calculate the y-intercept by taking the x/y mean point from the beginning, in this case (3/4), and put it in the regression equation to easily find b0.
  4. State the final regression equation for that case by fillin in slope and intercept. p.e. ŷ=1.6+0.7x
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3
Q

What is the simple linear regression equation?

A

ŷ = b0 + b1*x

ŷ=the predicted value of y (the dependent variable) in a regression equation.
b1=slope
b0= y-intercept

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4
Q

What does R-squared tell us?

A

How well a regression line actually predicts the values 1.0 would be the perfect prediction.

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5
Q

How to calculate R-squared?

A
  1. Take the linear regression equation (with intercept and slope calculated) at hand. P.e. it could be ŷ=1.6+0.7x
  2. Put in the x values of your points in the equation and calculate ŷ.
  3. Now put everythin in the formula of R-squared

Sum(ŷ-ymean)2
______________
Sum (y-ymean)
2

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