Unit 8 - Correlation & Regression Cartes | Quizlet

What does a scatter graph reveal?

The relationship between X and Y (how they affect each other)

How to create a scatter graph in Excel

Highlight all the data of both columns (not the titles), click 'Insert', then 'Scatter', then choose type '1' - it will automatically produce this for you

How to label the axes on a scatter graph in Excel

Click the '+' found at the right side of the scattergraph, then click 'Axes labels', then label them (by double clicking them & typing the names in)

What is the independent variable?

A variable that is the reason why the dependent variable changes

What axis does the independent variable go across?

The X-axis

What is the dependent variable?

The variable that is being measured or tested (to see a correlation)

What axis does the dependent variable go across?

The Y-axis

How to add a regression line to a scatter graph in Excel

Click the scattergraph - on the ribbon, click 'Chart design', then click 'Add Chart Element', then 'Trendline', then 'Linear'

What is correlation?

Shows how two variables are linked (based on how they go up/down with each other)

What is positive correlation?

As one value increases, the other value increases (& vice versa)

How can you see that it is positive correlation?

The regression line goes up diagonally (as the X axis increases, the Y axis increases)

What is negative correlation?

As one value increases, the other value decreases (& vice versa)

How can you see that it is negative correlation?

The regression line goes down diagonally (as the X axis increases, the Y axis decreases)

How can you see that there is little/no correlation

You can't really draw a line at all because the results are dotted all over the place

What is the correlation coefficient?

A number stating the relationship between two variables (between -1.0 & 1.0)

What does a positive correlation coefficient mean?

It is positive

What does a negative correlation coefficient mean?

It is negative

What does 0 mean for the correlation coefficient?

There is no correlation

When is a positive correlation stronger?

It is closer to 1 (it is closer to a perfectly diagonal line)

When is a negative correlation stronger?

It is closer to -1 (it is closer to a perfectly diagonal line)

When is a correlation weaker?

It is closer to 0 (the line is less strong or diagonal)

What type of correlation coefficient are we studying?

Pearson's Product Moment Correlation Coefficient (R)

How to calculate the correlation coefficient using cell referencing

=CORREL(the range of Y, the range of X)

What does a straight line equation help us find?

Results that aren't on the scatter graph (based on the regression line)

How to calculate the straight line equation

y = a + bx

What does the 'a' stand for in a straight line equation?

The Y intercept

What does the Y intercept tell us?

The value of Y when X = 0

How to calculate the Y intercept using cell referencing

=INTERCEPT(the range of Y, the range of X)

What does the 'b' stand for in a straight line equation?

The gradient (slope)

What does the gradient (slope) tell us?

How much Y increases for a unit increase in X

How to calculate the gradient (slope) using cell referencing

=SLOPE(the range of Y, the range of X)

What does the 'x' stand for in a straight line equation?

The independent variable (which you use to multiply by the slope in the regression equation)

What is 'y = a + bx' also known as?

The estimated regression equation

What does it mean when a value is meaningful?

It is a relevant number to the value (it doesn't have significantly more/less figures, it is a minus number etc)

What does it mean when a value is reliable?

When the independent value (X) comes within the range of the lowest to highest data values

What is interpolation?

When you predict a value inside the range of data points

What is extrapolation?

When you predict a value outside the range of data points

What is the correlation of determination (R^2)?

The square of the correlation coefficient

What does the correlation of determination (R^2) show?

How much the variation in the Y value can be explained by the variation in the X value

How to calculate the correlation of determination (R^2)?

Square the correlation coefficient

How to square the correlation coefficient in Excel

=(correlation coefficient^2)

How to find the correlation of determination (R^2) using cell referencing

=RSQ(the range of Y, the range of X)

How is the correlation of determination (R^2) shown?

As a percentage (so you must multiply it by 100 or change it to a percentage on Excel)