Differential attrition can threaten the internal validity of a ...

[fagboi]

Differential attrition can threaten the internal validity of a between-subjects experiment.
 
  a. True
  b. False
  Indicate whether the statement is true or false

Question 2

What is test-retest reliability and how is it measured?
 
  What will be an ideal response?

[britb2u]

Answer to Question 1

True

Answer to Question 2

You estimate test-retest reliability when you administer the same test to the same (or a similar) sample on two different occasions. This is a classic way to check on the stability of a measure. This approach assumes that there is no substantial change in the construct being measured between the two occasions. In estimating test-retest reliability, the focus is on analyzing the data collection instrument as a potential source of error. The amount of time allowed between measures is critical. You know that if you measure the same thing twice, the correlation between the two observations will depend in part on how much time elapses between the two measurement occasions. The shorter the time gap, the higher the correlation; the longer the time gap, the lower the correlation, because the two observations are related over time; the closer in time you get, the more similar the factors that contribute to error. Since this correlation is the test-retest estimate of reliability, you can obtain considerably different estimates depending on the time interval. Ideally, the interval between the two observations should be long enough so that values obtained the second time around are not affected by the previous measurement (for example, the respondent may just simply remember his or her response if the time interval is too short) but not so distant that knowledge of new things over time alters the way the study participants responds to the question.