Validity- assessing and improving.

Validity is whether a test or measure actually measures what it was intended to.

Different types of validity:

Internal- whether changes in the DV is due to the manipulation of the IV and not other factors.

External- can a study generalise to other settings, people and eras.

• Ecological validity- type of external validity and it refers to generalising findings to real life.
• Temporal/historical validity- type of external validity and it refers to if research from one time period can be applied to another accurately.
• Population validity- type of external validity and refers to whether research can be generalised to other people/populations. 

2 ways to assess validity.

1) Concurrent validity- where performance on one test correlates highly with performance on another test of the same variable. 

2) Face validity- where a study appears on the face of it to represent what is being measured. 

Improving validity of experiments:

• Use standardised procedure and instructions which reduce the effects of situational variables, particpant variables and experimenter bias. 
• Use either a single or doubled blind procedure which reduce effects of particpant variables because they are not aware of aims and cannot change their behaviour (demand characteristics) and it also reduces experimenter bias because they too are unaware of the true aims and their behaviour will not influence the participants in any sense. 
• Repeated measures have the problem of order effects to limit this effect the researcher can used counterbalancing so that the 2 conditions are tested 1st and 2nd in a random order. 
• Independent groups have the risk of participant effects to limit these effects participants must be randomly alloacted. 

Improving validity of questionnaire:

• Incorporate a lie scale to control for social desirability bias. This is statements which is the same but phrased in a different way and if answered differently the questionnaire is not valid.
• Make sure the participants are aware that the data they submit is anonymous which will make participants more likely to be honest with their answers and provide valid information about a certain experience.

Improving external validity:

• Ecological validity- repeat in a different settings and make a task as close as possible to real life so it will be generalisable.
• Population validity- use either a larger sample or a different sample to see if the results are representitive. 
• Temporal validity-repeat a historical study and compare results to see if they results are still valid such as Asch's study was called a 'child of it's time'.