survey #3

to obtain a representative data set to generalize to the population

-probability sampling

- nonprobability sampling

• -relies on chance to determine inclusion in sample
• *anyone can become a participant

**this type of sample is preferred

-sample selected in other ways

*ask people you know or random people at the mall

the stability or consistency of our measurements

• nonsystematic mistakes in measurement
• *ex: misreading a questionnaire item
• *observer looks away when coding behavior
• *nonsystematic misintrepretations of a behavior

-consistency of measurement

• -consistency can be conceptualized in different ways
• *therefore there are different types of reliability

• -usually measured in correlation
• *should be a positive correlation

degree of agreement between two independent raters

degree of consistency over time

degreee to which the items of a measure all measure the same thing

• -reliability is a measure of consistency
• ***perfect reliability means that the scores are perfectly consistent

-reliability deteriorates when the consistency is lost

-the rank of orderings are still reasonably consistent

- as reliability deteriorates further, the rank orderings from the two testings are less similar

• -when you reach the point where the rank orderings have no relationship to one another, your reliabilty is poor
• *new test would administer a different pattern of results