Week 5 Flashcards
What are signs of mistakes in correlations ?
Data points a long way away
Perfect straight line
No relationship at all
What is a Correlation?
Correlations measures/shows the relationship between two groups/vraiables
What is the line of best fit?
It represents an approximation of the most close relationship between the two groups/variables in a correlation scatter plot and highlights any trends to allow for predictions
What are residuals ?
Difference between observed and predicted values, it shows the distances the data has deviated from the best of fit line, therefore smaller = better fit
Correlation coefficient equation ?
R = Sxy/Sx.Sy
Sxy = how much x and y change together
Sx.Sy = how much they change separately
What does the R-value tell you?
Above 0 = Positive correlation
Below 0 = negative
Close to 1 = strong
Close to 0 = weak
What does the r^2value tell you?
Close to 1 = lot of variance
Close to 0 = only a little variance
What is regression?
Analysing of the relationship between the DV with one or more IV to predict the DV and quantify relastionships between these variables
Differences between Correlation and Regression?
C - describes single relationships where R - describes multiple.
C - focuses on the strength and direction of the relationship, R - focuses on strengthS directionS
C - X and Y are interchangeable, R - They are NOT
C - r and r^2, R - r, r^2, F, t, SE, ß1-n
C - does not allow prediction, R - does.
What should you do immediately after collecting data?
Plot into a graph and view
Who suggested the first approach for determining relationship between groups? Time?
Francis Galton
1880s
Definition of slope in regression?
How much change in x-axis affects change in y-axis (measurements)
Definition of intercept in regression?
The point on the y-axis where the line of best fit passes through
