Correlation Flashcards
What is correlation?
Measures and descriptions of the relationship between two variables.
What are the three main characteristics of relationships in correlation?
- Direction (negative or positive)
- Form (linear is most common)
- Strength (varies from 0 to 1)
What does a positive correlation indicate?
As one variable increases, the other variable also increases.
What does a negative correlation indicate?
As one variable increases, the other variable decreases.
What is the Pearson correlation coefficient (r)?
Measures the degree and direction of the linear relationship between two variables.
What correlation value indicates a perfect linear relationship?
-1.00 or +1.00.
What does the sum of products (SP) measure?
The amount of coverability between two variables.
How can the Pearson correlation formula be expressed?
As a relationship of z-scores.
True or False: Correlation demonstrates causation.
False.
What is the coefficient of determination?
Measures the proportion of variability in one variable that can be determined from the relationship with the other variable.
What is the null hypothesis (H0) in correlation testing?
H0: ρ = 0.
What does a partial correlation measure?
The relationship between two variables while controlling the influence of a third variable.
What is the Spearman correlation used for?
Data from an ordinal scale (ranks) or when both variables are consistently directional but may not be linear.
Fill in the blank: The _______ correlation measures the relationship between two variables where one variable has only two values.
Point-biserial.
What is the Phi coefficient used for?
Both variables are dichotomous.
What does a larger r value indicate?
A stronger correlation.
What is the effect size of an r value of 0.90?
81%.
What does the term ‘outlier’ refer to in correlation analysis?
An extremely deviant individual in the sample.
What is the impact of a restricted range of scores on correlation coefficients?
It may produce a very different correlation than would a broader range of scores.
What are the steps in hypothesis testing for correlation?
- State the hypotheses
- Determine alpha and critical value
- Compute the Pearson r
What is the significance of a correlation of 0.6 compared to 0.3?
0.6 (r² = 0.36) is more than twice as strong as 0.3 (r² = 0.09).
How do you handle tied scores in Spearman correlation?
Compute the mean of their ranked position and assign this mean value as the final rank.
What is the formula for calculating the Spearman correlation?
Use D as the difference between X rank and the Y rank for each individual.
