Flashcards
Stats Lecture 7/8 - Correlations
Cards in this deck (10)
- 1Elements of a correlationA correlation coefficient:
quantifies how well the best fit line explains the data
gives direction of relationship.
A correlation has two features
Magnitude
direction
A correlation of zero shows no relationship. - 2Charactersitics of a correlationMagnitude:
Between 0 and 1.
A value of ‘0’ means no relationship.
A value of ‘1’ means a perfect relationship.
Direction:
Negative Correlation vs. Positive Correlation.
For example, -.67 or .56. - 3CovarianceA numerical estimate of how much the two variables (X and Y Covary)
Like variance formula but with the inclusion of Y - 4Correlation CoefficientA standardized value of the correlation between to vriables
Most common calculation: Pearson’s correlation coefficient/Pearson’s product-moment correlation
A score between 0 and 1, and a direction
Score indicates strength of relationship/ steepness of the line of best fit - 5Calculating the correlation coefficient(∑(
- 6What is Coefficient of Determinaionr^2 value tells you exactly how much variance they share
- 7Sumary of Correlation coefficientsTells us the strength and direction of a relationship between two variables
0-1: Closer to 1 indicates stronger link
Check a scatterplot for outliers/non linear relationships
Break the formula down when computing Pearson’s by hand
Correlation does not equal causation - 8Pearson's Coefficient (Paramatretic)There's always a parametric test and a non-parametric equivalent,
Paramatric - you make certain assumptions about the qualities of your data; needs to be ordinal or ratio, cannot be nominal
homogenaeity of variance; variance of two variables shouldn't be too different - 9Spearmanh's Rho (the non-paramtetric version of correlation coefficientsIf you have nominal data but still want to determine correlation, use Spearman's Rho.
- 10How to Calculate spearman's Rhothe same as the Pearson's correlation coefficient, just using rankings instead of scores
(∑(
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- Flashcards on Stats Lecture 7/8 - Correlations, created by sarahderveeuw on 18/05/2015.
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