threats to internal validity

Question 1

selection

Answer 1

occurs when groups are not equivalent from the beginning, they differ in some variable

Question 2

history

Answer 2

when outside events happen to participants during the experiment

can influence the dv

Question 3

maturation

Answer 3

participants go through natural development during the experiment

Question 4

testing effect

Answer 4

when the first measurement of the dv may affect the second measurement

Question 5

instrumentation

Answer 5

when the instrument measuring the dv changes slightly between measurements

Question 6

regression to the mean

Answer 6

when the initial score of the dv is either too low or too high
have a statistical tendency to become more average on the following trials

Question 7

experimental mortality

Answer 7

when some participants drop out during the experiment (not randomly)

Question 8

demand characteristics

Answer 8

when the participants understand the purpose of the study and change their behavior to fit the experiment

Question 9

experimenter bias

Answer 9

occurs when the experimenter influences the study unintentionally