Is this an experiment?

1. 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. Today’s session

3. In a true experiment... • 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. The effect of stress on errors True experiment High stress condition PPs randomly allocated to two conditions Number of errors measured Low stress condition Based on Coolican (2001)

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

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

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

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

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

10. High internal validity Low ecological validity High ecological validity Low internal validity