Correlation Flashcards
Positive correlation
as x increases, so does y
negative correlation
as x increases, y decreases
correlation coefficient
r
what is correlation
how well the points in a graph suggest a pattern
r = 0
no correlation between x and y
r = 1
perfect positive correlation
- as r gets closer to 1 the more perfect the correlation is
r = -1
perfect negative correlation
- as r gets closer to -1 the more perfect the correlation gets
line of best fit
used to make predictions
aka regression line
extrapolation vs interpolation
if the line of best fit is used to make a prediction, and y is in the boundaries of the data than it is reliable. and is called interpolation
if y is outside of the data, then this is not reliable and is called extrapolation
how to find y from x
use line of best fit
how to find x from y
not possible
mean
always contained in the line of best fit
calculator to find line of best fit
go to stat, enter data
go back to stat, go to 4
press calculate
r = correlation
a = x
b = y
how to graph a line from a scatter plot
find the gradient from two points
then use one point as x and y to find c
gradient
the amount of ____ that declines/increases in relation to ____
(changine in y/change in x)
example of analysis of gradient
the length of a band stretching with every weight added
the score on the test in relation to the hours studied
y intercept in a problem examples
- the test score when the hours studied is zero
- the length of the band stretched when the weight is zero
- (y when x is zero)
How to describe correlation
positive/negative
strong/moderate/weak
linear/non linear
How to predict using line of best fit
- find the equation of the line
- plug in the x coordinate as the number you are using to predict
- find y
units of gradient
y/x
If the x decreases by ____ how would the y change
- y/-____ = gradient
- multiply gradient by ____
what makes gradient strong/moderate/weak
strong < 0.75
0.55 < moderate < 0.75
weak > 0.55
