Covariance Flashcards
If scores for one variable change then the scores for the other variable also change in a predictable manner
What term is used to describe this?
High covariance
Changes in one variable are not accompanied by a predictable change in the other variable
What term is used to describe this?
Low covariance
What is covariance?
A measure of how much two variables vary together
Low covariance is…?
Changes in one variable are not accompanied by a predictable change in the other variable
High covariance is…?
If scores for one variable change then the scores for the other variable also change in a predictable manner
What is the formula for total covariance?
(x coordinate - mean of x variable) x (y coordinate - mean of y variable)
Repeat this depending on how ever many coordinates there are
And add all of the results together
What is the formula for sample covariance?
Total covariance / (sample size - 1)
What describes how much two variables (x, y) co-vary (the amount of variance they share)?
Sample covariance
What is positive covariance?
Indicates that higher-than-average values of one variable tend to be paired with higher-than-average values of the other variable.
What is negative covariance?
Indicates that higher-than-average values of one variable tend to be paired with lower-than-average values of the other variable.
What is zero covariance?
If the two random variables are independent, the covariance will be zero. (However, a covariance of zero does not necessarily mean that the variables are independent. A nonlinear relationship can exist that still would result in a covariance value of zero.)
Indicates that higher-than-average values of one variable tend to be paired with lower-than-average values of the other variable.
This is known as…?
Negative covariance
Indicates that higher-than-average values of one variable tend to be paired with higher-than-average values of the other variable.
This is known as…?
Positive covariance
If the two random variables are independent, the covariance will be zero. (However, a covariance of zero does not necessarily mean that the variables are independent. A nonlinear relationship can exist that still would result in a covariance value of zero.)
This is known as…?
Zero covariance
How do you find the variance when you’re given only the s.d.?
Square the s.d.
What is the formula for variance?
(x coordinate - mean of x variable) ^2 / (sample size -1)
Data are collected for three participants on two variables (X, Y). The data are described below:
P1: (1, 3)
P2: (2, 4)
P3: (3, 5)
a) The mean for variable X is:
b) The mean for variable Y is:
c) The sample covariance of the X and Y data is:
a) 2.0
b) 4.0
c) 1.0
Data are collected for three participants on two variables (X, Y). The data are described below:
P1: (2, 6)
P2: (4, 8)
P3: (6, 10)
a) The mean for variable X is:
b) The mean for variable Y is:
c) The sample covariance of the X and Y data is:
a) 4.0
b) 8.0
c) 4.0
