1 / 9

Non-Experimental Data: Natural Experiments

Non-Experimental Data: Natural Experiments . Natural Experiment (No control over experimental stimulus). 1. Choose an IV 2. Choose a DV Locate a convenient sample that is due to be exposed to a naturally occurring stimulus (IV) (experimental group)

larya
Download Presentation

Non-Experimental Data: Natural Experiments

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Non-Experimental Data:Natural Experiments

  2. Natural Experiment (No control over experimental stimulus) 1. Choose an IV 2. Choose a DV • Locate a convenient sample that is due to be exposed to a naturally occurring stimulus (IV) (experimental group) • Locate a convenient sample that is NOT due to be exposed to that naturally occurring stimulus (IV) (control group) 5. Collect data on the DV from both populations (pre test). 6. Wait for the naturally occurring IV stimulus to affect the experimental group. 7. Collect data on your DV from both populations (post test). 8. Compare and analyse the two sets of results.

  3. Natural/ ‘Quasi’ Experiments • Used to refer to situation that is not experimental but is ‘as if’ it was • Not a precise definition – saying your data is a ‘natural experiment’ makes it sound better • Refers to case where variation in X is ‘good variation’ (directly or indirectly via instrument) • A Famous Example: London, 1854

  4. Snow- Cholera Epidemic

  5. The Case of the Broad Street Pump • Regular cholera epidemics in 19th century London • Widely believed to be caused by ‘bad air’ • John Snow thought ‘bad water’ was cause • Experimental design would be to randomly give some people good water and some bad water • Ethical Problems with this

  6. Soho Outbreak August/September 1854 • People closest to Broad Street Pump most likely to die • But breathe same air so does not resolve air vs. water hypothesis • Nearby workhouse had own well and few deaths

  7. Why is this a Natural experiment? • Variation in water supply ‘as if’ it had been randomly assigned – other factors (‘air’) held constant • Can then estimate treatment effect using difference in means • Or run regression of death on water source distance to pump, other factors • Strongly suggests water the cause • Woman died in Hampstead, niece in Islington

  8. Other examples: • Christianson and Hubinette (1993) Their experiment on anxiety • The influence of tv on aggressive behaviour • (Charlton et al., 2000) (Williams, 1986)

  9. TASK! In pairs, Read the examples of natural experiments in your books on page 84 and answer 3.11

More Related