urgent- sac transformations

[sjayne]

So for my further sac we have to draw three different scatter-plots and then choose one to transform. My question is, which scatter-plot should I choose( the one with a higher gradient or lower gradient or r^2) and also how do you know which transformation to use once you choose a graph? The end of the sac is tomorrow so immediate answers would be brilliant

[Yacoubb]

So for my further sac we have to draw three different scatter-plots and then choose one to transform. My question is, which scatter-plot should I choose( the one with a higher gradient or lower gradient or r^2) and also how do you know which transformation to use once you choose a graph? The end of the sac is tomorrow so immediate answers would be brilliant

You would choose the scatter plot that is MOST non-linear (i.e. residual plot pattern/no pattern), has the lowest Pearson Correlation Coefficient value (i.e. relationship between IV and DV is weakest) and has the lowest Coefficient of Determination (i.e. not reliable to predict DV from the IV). These factors should ALL be taken into consideration; but if you have two linear scatter plots and one non-linear scatterplot, you'll obviously apply transformation to this.

Okay so this is where your circle of transformations comes in handy. Actually, you should DEFINITELY have this in your bound reference. The circle of transformations enables you to compare the shape of your scatterplot to the side of a circle (i.e. circle of tranformations) and choose a particular transformation. Now the thing is, you may be able to apply more than 1 type of transformation. If you are asked to see which is the BEST, you consider the following factors:
* Residual Plot (most appropriate transformation yields most random residual plot).
* Pearson's Correlation coefficient (most appropriate transformation yields strongest relationship between the IV and the DV).
* Coefficient of Determination (most appropriate transformation enables you to most strongly predict the DV from the IV.

Circle of Transformations:
http://www.vcefurthermaths.com/2011/03/data-transformations/

^ Watch this video and it'll help you to visualise + understand how to interpret your circle of transformations on the SAC. Sorry for the late reply!