Chapter Objectives

  • Recognize and differentiate between key terms.
  • Apply various types of sampling methods to data collection.
  • Create and interpret frequency tables.

Assignment

Variables

  • In a randomized experiment, the researcher manipulates the explanatory variable and then observes the response variable
  • A group of people who take vitamin E are healthier and group that doesn’t, isn’t as healthy
  • Does that mean vitamin E is good for you?
  • The group that takes vitamin E likely also does other healthy things
  • Variables that can cloud a study are lurking variables

Experiment Design

  • Experiments must be designed to isolate the explanatory variable
  • Lurking variables spoil this
  • You can’t get rid of them, but you can average them out
  • ! Need adequate experimental units (subjects)
  • ! Need random assignment of subjects to treatment groups

Placebos

Results showed that believing one had taken the substance resulted in times almost as fast as those associated with consuming the substance itself. In contrast, taking the substance without knowledge yielded no significant performance increment.

McClung, M. and Collins, D. (2007 June). “Because I know it will!” Placebo effects of an ergogenic aid on athletic performance. Journal of Sport & Exercise Psychology, 29(3), 382-94. https://pubmed.ncbi.nlm.nih.gov/17876973/

  • Power of suggestion can’t be ignored
  • To combat this, control groups are given a placebo treatment, an inert substitute
  • If you don’t tell them, they are blinded
  • If you also don’t tell the researchers, it’s double-blind

Ethics

  • Studies shape policy and human behavior
  • Don’t manipulate data
  • Be transparent
  • And don’t harm your subjects
  • Want to see how malnutrition affects children?
  • Set up an observational study
  • You won’t be able to control your variable, but careful planning and sorting can yield the what you are looking for