Research methods and statistics

 Internal validity is concerned about the causal-effect relationship in a study ◦ Can observed changes be attributed to your programme/intervention or are the results influenced by alternative causes?

 Three types of threat: ◦ Single groups ◦ Multiple groups ◦ Social interactions

 History – some historical event that occurred  Maturation – events over time that aid learning  Testing – pre-testing primes the participants for what is to come (practice effect)  Instrumentation – is there any difference in the pre-test/post-test instrument. What information do we have on reliability, or has the instrument been modified  Mortality – have any participants dropped out  Regression- pre-test scores are always likely to improve on a post-test

 Have a control group that does not have the programme/intervention ◦ Placebo effect in medical trials

 Selection bias – the degree to which the groups are comparable before the study ◦ Selection history threat ◦ Selection testing threat ◦ Selection maturation threat ◦ Selection instrumentation threat ◦ Selection mortality threat ◦ Selection regression threat

 Conduct a randomised or true experiment

 Diffusion of treatment – participants share their experiences with other participants  Compensatory rivalry – groups try and compete with one another  Resentful demoralisation - the comparison group under achieves due to jealousy with the other group  Compensatory equalization of treatment - the researcher tries to make one or both groups feel special

 External validity is concerned with generalisation ◦ Can you generalise your results to a wider population  Sample modelling – you first identify the population you want to generalise to and then draw a sample from that population  Proximal similarity (Gradient of similarity) – identify populations that are more or less similar to the original study

 Unusual people  Unusual places  Unusual times

 Use a random sample  Keep drop out rates low  Replicate the study with different people at different times in different places

 Electronic resources are available from ◦