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| Question | Answer |
| Reliability and validity | -psychologists who are committed to using scientific methods in their research investigations try to design studies that can be replicated or repeated. -to achieve this, it is vital that the measurement tools used in an investigation are reliable and that the data they produce are valid. |
| Reliability | The extent to which a method of measurement or test produces consistent findings. -replicate study to check for consistent results |
| Validity | -in addition to our measurements being consistent, they also need to be valid. -validity means that we are actually measuring what we claim to be measuring. -whether it has tested what was set out to be measured. -there are 2 broad categories of validity 1. internal validity 2. external validity |
| Internal validity | -the validity of an experiment in terms of the context in which it is carried out. -concerns events within the exp as distinct form external validity. |
| External validity | -the validity of an exp outside the research situation itself; the extent to which the findings of a research study are applicable to other situations, especially 'everyday' situations -External validity is affected by internal validity- you cannot generalise the results of a study that was low in internal validity because the results have no real meaning for the behaviour in question. |
| Experimental validity | 2 types 1. internal validity 2. external validity 1. internal- refers to inside the study e.g. the measurements tools, procedure 2. external- concerns what goes on outside the exp e.g. it is about representativeness and generalising. |
| Types of Internal validity Assessing internal validity | 1. Face 2. Concurrent 3. Predictive 1. face validity- assess validity by asking yourself if the test looks as if it could/is measuring what it is suppose to (e.g. a tape measure isn't going to measure IQ, only the size of your head). 2. concurrent validity- involves comparing the results found in a new test with those from an existing, already well established test that has good validity. (e.g. score 148 on an established test, but only 110 on the new one- this raises Q's on the validity of the new test. 3. predictive validity- the ability that a test can predict performance on future tests e.g. performance on your GCSE tests should help to predict the type of grades you are capable of achieving at A level. |
| Type of External validity Assessing external validity | 1. Population 2. Ecological 1. population validity- whether the findings can be generalised to the people outside of the sample population. 2. ecological validity- how true to real life were the findings, could they be generalised to other settings. |
| Internal valditiy being affected | - extraneous variables can affect internal validity if the extraneous variables aren't controlled properly, then they could directly affect the DV's, but we only want the IV affecting the DV. -if a study doesn't have face value, concurrent (concur- agree) and predictive validity the validity is very low. |
| More on external validity | -the sampling method can affect population validity because the findings may not be a generalisation to other people outside of the sample population. -choice of method- this can affect the ecological validity because the method chosen may be quite artificial, so isn't very true to real life findings. -so the method needs to be able to be generalised to other settings. |
| external validity | -the more you can replicate a study, in different settings, with different people, in varying time periods, the higher the external validity becomes. |
| Examples of external validity | 1. population- Milgram (1963) lacked population validity 2. Ecological- Asch (1940) wouldn't be generalised as being a normal everyday life activity. - artificial - lacks ecological validity. - a lot of exp's that are lab exp are low in ecological validity. 3. historical- Dement and Kleitman (1957) and Milgram (1963) |
| Types of Reliability | Internal -refers to what is going on inside the study -e.g. do all of the Q's on a questionnaire measure the same thing? External -refers to outside of the study -e.g. observations are repeated. -similar/consistent results each time in a test outcome. |
| ways of assessing reliabilitiy | Internal split half method -this is to compare a person's performance on 2 halves of a questionnaire or test. -if the test is assessing the same thing in all its Q's then there should be a close correlation in the scores derived from both halves of the test. External Test-retest -where a person is given a questionnaire/interview/test on 1 occasion and then this is repeated again after a reasonable interval (e.g. week/month) -if the measure is reliable, the outcome should be the same every time. observer (inter rater) reliability -observers use the same behavioural category check list and observe the same event separately -you can then compare their findings to see how similar they are |
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