====== Interaction Effects in Multiple Regression Analysis ======
[[http://www.ats.ucla.edu/stat/spss/webbooks/reg/chapter1/spssreg1.htm|Ch. 1. Regression with SPSS]] \\
[[http://www.ats.ucla.edu/stat/spss/webbooks/reg/chapter7/spssreg7.htm|Ch. 7. Regression with SPSS]] \\
http://psych.unl.edu/psycrs/statpage/quantint.pdf \\
http://quantpsy.org/interact/interactions.htm \\ 
http://essedunet.nsd.uib.no/cms/topics/regression/7/2.html \\


https://www.youtube.com/watch?v=l3Aoikhaxtg \\
https://www.youtube.com/watch?v=aeT8MkG3bx8 \\
https://www.youtube.com/watch?v=aVV7KnAr-qY \\
https://www.youtube.com/watch?v=vYsjJpyrHFc \\
https://www.youtube.com/watch?v=SdOrkPn7d8Y \\


https://statistics.laerd.com/spss-tutorials/ancova-using-spss-statistics.php
  * see #9.
http://www.ats.ucla.edu/stat/spss/whatstat/