1. psychlotron.org.uk Is this an experiment? A researcher wanted to investigate the effect of gender on driving ability when talking. She recruited a group of male and female university students and matched them for how long they had held a driving licence for and how far they drove each week. She measured the number of collisions they made operating a driving simulation whilst responding verbally to a verbal reasoning task.

2. psychlotron.org.uk Today’s session You will learn aboutContext Quasi experiments and group comparison studies Identifying & distinguishing between experiments and non-experiments Internal-external validity tradeoffs in experimental design Studies of social and cognitive psychology and individual differences

3. psychlotron.org.uk In a true experiment... – An IV is manipulated in a controlled manner – Extraneous variables are controlled – A DV is measured to see if it changes Quasi-experiments share features with true experiments, but do not meet all of these criteria

4. psychlotron.org.uk The effect of stress on errors True experiment PPs randomly allocated to two conditions High stress condition Low stress condition Number of errors measured Based on Coolican (2001)

5. psychlotron.org.uk The effect of stress on errors Quasi experiment High stress condition Low stress condition Number of errors measured Based on Coolican (2001) Night shift Day shift

6. psychlotron.org.uk The effect of stress on errors Group difference study Questionnaire used to identify... High stress PPs Low stress PPs Number of errors measured Based on Coolican (2001)

7. psychlotron.org.uk Why would a researcher prefer to use a true experiment over a quasi experiment or group difference study?

8. psychlotron.org.uk Given their limitations, what justification is there for using quasi experiments and group difference studies?

9. psychlotron.org.uk Validity tradeoffs Increased control over the research situation increases the internal validity Increased realism in the research situation increases the ecological validity

10. psychlotron.org.uk High internal validity Low internal validity Low ecological validityHigh ecological validity