What is Validity?
Validity refers to the extent to which a measure is measuring what it intends to, or in other words, it refers to extent to which it reflects the reality that it claims to represent. The first definition is more relevant to internal validity, whilst the latter helps to explain external validity.
How many types of validity are there?
In short, loads. But out of ones that you should know at A-level, there's two categories, and a couple of types under each heading.
Internal validity: the extent to which a measure or test is measuring what it intends to. There are typically thought to be three main types:
1. Face validity - validity at face value, the simplest form. It's basically what gets affected by confounding and extraneous variables and lack of control over these factors.
2. Construct validity - is the IV or DV appropriate for the concept being investigated? For concepts such as stress, this is a major issue. How do you define stress? And how can it be properly measured if there's no standard definition? One study which is relevant from the clinical psychology bit is Lewinson's study on positive reinforcements and depression - can you really measure depression levels on a depression adjective checklist?
3. Concurrent (criterion) validity - do other relevant measures get the same result as yours? For example, if you're intending to measure intelligence through a new method, do the IQ scores or school performances of your participants correlate with the results you're getting?
External validity: the extent to which a measure or findings reflect the reality that it claims to represent. Again, there are 3 main types:
1. Ecological validity - refers to how realistic the task and environment is. If your task is similar to the real life behaviour it's attempting to measure, it's going to have high ecological validity.
2. Population validity - refers to how relevant the population is. If you're attempting to generalise your findings to all eyewitnesses, for example, you should ideally have a wide variety of real-life witnesses, who vary in age, gender, occupation, intelligence, ethnicity, etc.
3. Temporal validity - refers to how relevant the time period is in affecting the findings. e.g. A study on attitudes conducted decades ago cannot be expected to have temporal validity due to how quickly attitudes shift in society.
All of these essentially link back to generalisability, usefulness and applicability to real life situations, so it's a really useful issue to get your head around, and worth mentioning if you can.
Showing posts with label usefulness. Show all posts
Showing posts with label usefulness. Show all posts
Wednesday, 29 May 2013
Thursday, 9 May 2013
Usefulness
Like many of the issues and key terms in psychology, we know the gist of this term but it's one that is pretty hard to answer in an exam situation. What does it mean, and what points can we make on usefulness?
Usefulness refers to whether a piece of research or a theory is useful, practical or applicable. A useful piece of research is one that can be accurately generalised to a wide population or the target population and benefit a number of people or causes.
Accurately generalised to a wide population. You can actually split this definition pretty cleanly into three evaluative points: internal validity, external validity (including population and ecological) and to what extent it takes a nomothetic approach.
Internal validity
It encompasses a number of individual factors, and you'll have to really think about it in terms of the question to know what part is relevant to evaluate. Most of the time, it's either face validity (is it measuring what it intends to measure?) or construct validity (is the definition in the research actually accurate? Often a problem with stress is that it's hard to define stress, and often it's operationalised in a way that isn't truly accurate). If either are poor, a study isn't going to be very useful.
External validity
There are three main types: ecological validity (conducted in a real-life situation, i.e. has mundane realism), population validity (representative, large sample) and temporal validity (whether the research is only really applicable at one time). If any of these are poor, it's not going to be as useful as we would ideally like.
Nomothetic
Nomothetic in psychology refers to a theory which can be assumed to be a general law or principle of behaviour. If it is, it's more likely to be useful. The more "exceptions to the rule" there are, the less it's going to be useful. For example, Loftus et al's theory about weapon focus is pretty nomothetic, as is the theory about hassles causing more stress than life events. Findings from research that aren't nomothetic and can only be applied to a small number of people or situations aren't very useful.
Usefulness refers to whether a piece of research or a theory is useful, practical or applicable. A useful piece of research is one that can be accurately generalised to a wide population or the target population and benefit a number of people or causes.
Accurately generalised to a wide population. You can actually split this definition pretty cleanly into three evaluative points: internal validity, external validity (including population and ecological) and to what extent it takes a nomothetic approach.
Internal validity
It encompasses a number of individual factors, and you'll have to really think about it in terms of the question to know what part is relevant to evaluate. Most of the time, it's either face validity (is it measuring what it intends to measure?) or construct validity (is the definition in the research actually accurate? Often a problem with stress is that it's hard to define stress, and often it's operationalised in a way that isn't truly accurate). If either are poor, a study isn't going to be very useful.
External validity
There are three main types: ecological validity (conducted in a real-life situation, i.e. has mundane realism), population validity (representative, large sample) and temporal validity (whether the research is only really applicable at one time). If any of these are poor, it's not going to be as useful as we would ideally like.
Nomothetic
Nomothetic in psychology refers to a theory which can be assumed to be a general law or principle of behaviour. If it is, it's more likely to be useful. The more "exceptions to the rule" there are, the less it's going to be useful. For example, Loftus et al's theory about weapon focus is pretty nomothetic, as is the theory about hassles causing more stress than life events. Findings from research that aren't nomothetic and can only be applied to a small number of people or situations aren't very useful.
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