is a branch of psychology aimed at the measurement of

individual differences

approaches to personality/individual differences assessments include:

(peer report)

in research labs, participants blind to what is being assessed so may raise ethical issues

ambiguous/meaningless stimuli to describe. difficult to score/interpret

and questionnaires

Cronbach 1957 claimed that there are two opposing camps in psychology

are two fundamental notions of

reduce the reliability of our measure

traits, states or characteristics other than the one we are trying to assess

furthermore we must take into consideration people have the tendency to agree with items,

some people never choose extreme items and interpretation of questions, therefore having

in a questionnaire is one way to deal with the issues described above.

there are two approaches to establishing construct validity:

the degree to which scores correlate with the variables they are supposed to correlate with

the degree to which test scores do not correlate with variables they are not supposed to correlate with

other types of validity like

is based on the correlation between predictor and criterion scores obtained at approx the same time and

if a measure appears to measure what it's supposed to measure (by face value) and lastly,

the degree to which scores predict future behaviour on a criterion variable (i.e. friendliness to students)

The Cronbach Alpa measures

it provides a close approximation of the square to the correlation between

the cronbach is influenced by two things

the bigger the better, smaller correlations increase the influence of random or

and also influenced by the number of times, the more the better