Dr. Riddle wants to examine how tax increases influence spen…

Dr. Riddle wants to examine how tax increases influence spending habits. He knows sales tax in Hogsmeade  will increase by 2% at the beginning of 2018. He then has 30 of the biggest retailers report their monthly gross every 3 months for 12 months prior to the tax increase and the every 3 months for the 12 months after the tax increase.  This is an example of what type of research design?

Peter Parker  is examining how sleep deprivation influences…

Peter Parker  is examining how sleep deprivation influences driving ability. He has participants stay up for 36 hours and then has them drive in a driving simulator that records driving errors. He has people report how many years they have had a driver’s license, so he can control for that factor in his analysis. This means that how long someone has had a driver’s license is a(n) ________________________