Extraneous Variables Starter What is meant by reliability

Extraneous Variables

Starter • What is meant by reliability? – What is internal reliability? – What is external reliability? • What is meant by validity? – What is internal validity? – What is external validity? • What is mundane realism?

Learning Objectives: 1) To develop an understanding of extraneous variables in psychological research. Success Criteria: 1) Complete pages 23 -24 of your booklet making notes on extraneous variables. 2) Complete your key terms glossary for the terms covered so far. 3) Make revision cards for topics covered so far.

Extraneous Variables • Sometimes there are variables which the psychologist has to take into account when an experiment is taking place…think about our chocolate and memory experiment… – Did we need to make any improvements to the study? – Did something other than the IV cause a change in the DV?

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Extraneous Variables Participant Variables • Age, intelligence, motivation, experience • Gender Situational Variables • • • Order effects Time of day Temperature Noise Investigator effects Demand characteristics Participant Effects • Hawthorne effect • Social desirability bias

Task • Complete the tables on page 23 of your booklet using page 94 -95 of the textbook. • We’ll read and highlight page 24 as a class

Past Paper Question • Some psychology students read about an experiment which suggested that organisation is a useful strategy for improving memory. The students carried out an experiment to investigate the effects of organisation on word recall. They made up a list of 50 items that could be bought in a supermarket. The participants were teachers at their school. One group of participants saw the words organised into categories such as fruit, vegetables, dairy products and cleaning materials. The other group saw the same words presented randomly. (a) Suggest one possible extraneous variable in this study. (1 mark) (b) Suggest one way in which the students could control for this extraneous variable. (2)

Mark Scheme (a) AO 3 = 1 mark • Extraneous variables are anything other than the independent variable that could affect the dependent variable. In this study they could include participant differences, environmental variables such as temperature or noise, and experimenter variables including the way in which the research is conducted. (b)AO 3 = 2 marks • The control must relate to the variable in (c). 1 mark for a brief suggestion. Second mark for some elaboration. For example, control for participant differences by making sure both groups are similar (1 mark). Control for participant differences by randomly assigning the participants to conditions (2 marks).

Revision Cards • Make sure that all of your revision cards are up-to-date • Fill in your key terms glossary with all words prior to today’s lesson

Discussion • A psychologist finds that there is a relationship between ice cream sales and crime. Whenever lots of ice cream gets sold in supermarkets and shops, the crime rate peaks. The psychologist concludes that ice cream must cause crime. • What extraneous variables does the psychologist need to consider?