Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
14 Cards in this Set
- Front
- Back
|
Scatterplot |
The primary tool for examining two-variable relationships when both variables are numerical |
|
|
When examining histograms, we look for Center, spread and shape. When studying Scatter Plots what do we look for? |
We look for Trend (which is like the center), strength (which is like spread) and shape. |
|
|
Trend |
The general tendency of the scatter plot as a scan from left to right |
|
|
Positive association |
Positive trend |
|
|
Negative association |
Negative trend |
|
|
Strong association and weak association |
A strong Association will show little vertical spread. A weak Association will show more vertical spread. |
|
|
Linear |
The simplest shape for a trend. |
|
|
correlation coefficient |
A number that measures the strength of the linear association between two numerical variables. The correlation coefficient makes sense only if the trend is linear and the both variables are numerical. The correlation coefficient, represented by the letter R, is always a number between -1 & + 1. If the value of R is close to - -1 or + 1, then the association is very strong. If R is close to 0, the association is weak. If the value of the correlation coefficient is positive, then the trend is positive, if the value is negative, the trend is negative. |
|
|
How to find correlation coefficient |
First find the average values of both numeric variables. Then determine the standard deviation for each. Next convert all of the points two pairs of Z scores and multiply them together. |
|
|
Does r measure slope? |
No it does not it Just measures Direction and strength. |
|
|
If you switch X & Y will it affect r? |
No it will not. |
|
|
Is are affected by adding a constant or multiplying by a positive constant? |
No |
|
|
Regression line |
A tool for making predictions about future observed values. |
|
|
Equation of a line |
Y = a + bx a: intercept b: slope |
