Aim: Review for Exam Tomorrow
Independent VS. Dependent Variable
•Response Variables (DV) measures an outcomeof a study
•Explanatory Variables (IV) explains or causeschange in the response variables
Example: What is the IV and DV?
Half of a group of third-graders was shown a film on“sharing,” while the other half was not shown thefilm. The attitudes of the students in both groupstowards sharing candy was then measured, andtheir mean scores were compared.
Examining Scatterplots
–To examine scatterplots, need to:
1. Look at overall pattern and find deviations (outliers)
2. Describe form (clusters), direction (+/- association)
and strength (weak/strong)
Example: Describe relationship between variables.
Correlation Coefficient
–Measures the strength of the linear relationshipbetween two variables
R vs R-Squared
•r value of the correlation coefficient
•Adjusted r square the relative predictedpower of a model between 0 and 1
–100% r square means perfect predictability (closerto 1, the better)
–Measure the quality of fit
Finding the equation of a regressionline
•A regression line is also known as the line of best fit
•Methods to finding an equation of the regression line:
or
a is the y intercept and b is the slope of the line
Accuracy of Predictions?
•The accuracy of the prediction form aregression line depends on how much scatterabout the line the data shows
•The regression line summarizes the patternbut gives only roughly accurate predictions