Reliability and Validity

Question 1

what are the two types of reliability?

Answer 1

across time, internal consistency

Question 2

how do you measure test-retest reliability?

Answer 2

administer the scale at two different time points and compare the correlation between the 2 scores

Question 3

how do you measure internal consistency?

Answer 3

chronbach’s alpha - the average of correlations for items split in all possible ways, the closer to 1, the higher the reliability

Question 4

what is a limitation of chronbach’s alpha?

Answer 4

it increases with the number of items, even if they items don’t correlate very well

Question 5

how do you decide which items you should keep?

Answer 5

calculate chronbach’s alpha, leaving 1 item out everytime, if the alpha improves then the scale is more reliable without it

Question 6

what are the types of validity?

Answer 6

content - items relate to the construct of interest and are comprehensive
criterion - operationalisation of the construct relates to other established tests of that construct
construct - items measure construct in a meaningful way (correlate highly with related measures and vice versa)