Reliability and Validity Research Methods

RECAP! OBSERVATIONAL METHODS  Create 3 behavioural categories for the following: - Observation of students when teacher leaves room - Observation of dogs on walk in the park - Observation of giraffes in the zoo

Learning Objectives  To define reliability  To define internal and external validity  To describe factors which can affect validity

Reliability  Linked to…  replicability – if the experiment was repeated, would the same results be found?

Improving Reliability  Standardised procedures – all researchers carry out process the same  Inter-rater reliability – more than one researcher to observe behaviour – are they interpreting it the same?  Training needed for all researchers

Validity  Accuracy of an experiment  Does it measure what it claims to?  Are the conclusions drawn justified?

Internal Validity  Ability of study to test the hypothesis  How sure are we that it is the IV causing the effects on the DV? (not extraneous variables)

External Validity  How well can results be generalised beyond the study?  Population validity – sample - can results be generalised to other groups of people?  Ecological validity – setting - can results be generalised to other situations?

Your Task  Complete the worksheet to determine whether the research is valid and why/why not   Dave – low population validity as only clientele from one shop being viewed – unlikely to be all ages and class/background. Also low ecological validity as it was only one shop that was observed so can’t be applied to “shopping” behaviour in general.   Jeannette – low internal validity – repeated measures design so order effects may me causing results rather than the affect of music on memory   Peter – low internal validity – network login does not mean they are working!!! Could be on games, chatting etc…

Factors which reduce internal validity: - Extraneous variables - Demand characteristics - Investigator effects - Social desirability bias

Extraneous variables  Anything other than the IV which affects the DV  E.g. participants mood

Demand Characteristics  Participants try to behave in the way they think is demanded (or against what they think is demanded)  Try to guess purpose of research – act in a helpful way  Act nervously/out of character as think they are being judged

Investigator effects  The researcher’s behaviour or characteristics influence the research in some way  Researcher bias – interpret behaviour in a way to fit their own views – pay more attention to data that confirms their expectations  Presence of observed – change behaviour of p’s  Characteristics of investigator – age, gender, appearance, facial expressions etc.

Social desirability bias  Participants want others to see them in a favourable way so respond or behave differently than they normally would  Might not give honest answers

Your Task  Decide whether the statements are examples of demand characteristics, social desirability bias or investigator effects.

Learning Check  Define reliability  State one way in which reliability can be improved  Describe the difference between internal and external validity  Describe one factor which can reduce internal validity. Provide an example of this.