Flashcards in Chapter 13 Correlation Deck (17):
What is a correlation?
A correlation is a relationship between two scale variables
What is a correlation coefficient?
a correlation coefficient is a statistic that quantifies a relationship between two variables.
What are the three main characters of the correlation coefficient?
The 3 main characteristics of correlation coefficient is 1) cc must be positive or negative, 2) cc always falls between -1 and 1, 3) the strength of the magnitude of the cc (not the sign) indicates how large the relationship is
What is a positive correlation?
A positive correlation is an association that people have high scores on one variable tend to have high scores on the other variable) If they have low scores on one, they will have low scores on the other
What is a negative correlation?
A negative correlation is an association that people who have high scores on one variable tend to have low scores on the other variable
When is a correlation perfect?
A correlation is perfect when all points fall in a straight line on a chart. Knowing someone's score on one variable means you also know their score on the other variable.
Correlation does not equal causation. What are the 3 possible explanations for causation?
1) the first variable caused the second variable 2) The second variable caused the first variable 3) A third variable could exist causing the first and second variable to occur
What are the sizes of the strength of the correlation?
The sizes of the correlation coefficient are 010 small, .30 medium, and .50 large.
When two variables are not related, what happens?
When two variables are not related, there is no correlation and they have a correlation coefficient close to 0.
What is the Pearson's Correlation Coefficient?
The Pearson's Correlation Coefficient is a statistic that quantifies a linear relation between two scale variables. A single number is used to describe the direction and the strength of the relation between two variables when their overall pattern indicates a straight line relation
What should be done before calculating the correlation coefficient?
A researcher must always create a scatterplot prior to be sure both variables are linearly related.
What two ways can the CC be used in statistics?
The Pearson CC can be used as a descriptive statistic to describe an association between variables; as an inferential statistic to see if a correlation is significantly different than zero.
If both deviations are above the mean line or both below the mean line, what does this mean?
If both are above or below the mean line, there is a positive correlation
If one deviation is above the mean line and the other is below, what does this mean?
If one is above the mean line and one is below, there is a negative correlation
What distribution does correlation fall under?
r distribution- distribution of correlations
How do outliers effect the correlation coefficient?
Outliers inflate the correlation