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Reliability and Validity (Types of Reliability (2) (Internal Reliability,…
Reliability and Validity
Types of Reliability (2)
Internal Reliability
Issues: More than 1 researcher - is there consistency in how they are interpreting behaviour or carrying out the study? More than 1 measure - if there is more than 1 test (such as used in a repeated measure design)then is there consistency of challenge in each test? *Within a measure - if a measure has more than 1 question (e.g. IQ test) or item (e.g. different words in a memory list or obstacles in a driving test) then are these questions/items consistently measuring the same thing
How to overcome issues :-clearly operationalise variables so there is less room for different interpretations. - Standardise the measure - i.e. make sure they are the same in difficulty etc. - Standardise each item or question within the study e.g. each word in a memory list has the same number of letters
How to assess/establish if reliable = Inter-rater reliability = all of the research carry out a pilot on the same Ppts, if they are 80%or higher in agreement then they are reliable. Pilot the different measures on the same Ppts without changing the conditions and then compare their scores to ensure consistency. Split-half = measure behaviour using 1st half of the test and then the 2nd half of the test using the same Ppts, if scores are similar then the test is consistent throughout
External Reliability
Issues : *Behaviour is only measured once = the test may not measure behaviour consistently at other times, e.g. a personality test may only indicate Ppts personality traits at the time the study was carried out.
How to overcome issues : Ensure tests etc. are designed in relation to measuring behaviours,attitudes etc. beyond one setting or time
How to assess/establish if reliable : Test-retest = the same Ppts repeat the same test at another time, e.g. 4 weeks later, to show consistency over time
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Validity
Internal Validity - Inside the study -is it measuring the effect of just the IV on the DV? - cause and effect cannot be established when lowering internal validity (e.g. EV, Demand Characteristics, Researcher bias, Investigator effects, Social desirability,Order Effects)
External Validity - Whether the findings can be generalised outside of the study to: the target population (below = low pop val) and (above = low pop val). The real life settings - ECOLOGICAL VALIDITY. Real settings and realistic tasks = high eco val. Controlled/artificial settings/tasks = low eco val
Types of Validity (2)
Internal Validity
Definition = The extent to which changes in a DV are legitimately caused by a change in an IV or is it by some other EV. Likewise in a correlation study is the strength of relationship legitimate or caused by EV.
Demand characteristics - (researcher favourable results received) and overcome by using single blind study - (don't inform Ppts aim of study)
Researcher bias - researcher interpretation of behaviour or the way they set up the study may be biased support their hypothesis thus to overcome issue you can use double-blind procedure = where both researcher and Ppts don't know aim of study
Social desirability = where ppt would change their answers from their natural behaviour to make them look cool and stand out and to overcome this you can ensure confidentiality = if Ppts believe that their behaviours or responses cannot be attribute to them they will more likely be truthful.
Test is inaccurate - measure used in study does not measure the desired behaviour, e.g. an IQ test that measures solely mathematical ability and to overcome issue use pilot-study = ensure test is accurate by trialling it with a focus group then consult with Ppts and make changes as needed
External validity
Definition : The extent to which the finding of the study can be legitimately generalised beyond the setting of a study
Ecological validity = the extent to which findings of study can be generalised to real life settings, often a problem for laboratory studies. Overcome issue by using design the study to be carried out in real life settings -field studies or natural experiments (form of quasi-experiment)
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