Diagramming Studies
You provide mints to a classroom of students and then measure their level of alertness.
X O
You let students choose whether they have a mint.
Selection Effect
Randomized control experiments typically have strong external validity. True or false?
False.
You allow students to choose whether or not they have a mint. Then you measure their level of alertness.
N X O1
N O1
You conduct a longitudinal daily study over two weeks to see if eating mints improves alertness. During the second week of the study, you change how you are measuring alertness.
Instrumentation
Large, representative surveys that use probability sampling typically have strong external validity. True or False?
True
You measure the level of alertness of a classroom of students every hour on the hour from 9am until 3pm. At 12:30pm, you provide everyone a mint.
O1 O2 O3 O4 X O5 O6 O7
You measure alertness every hour on the hour from 9am until 3pm, after providing everyone a mint at 9:30am. You notice that participant's alertness levels go down throughout the day on average.
Maturation
You measure alertness every hour from 9am to 3pm, providing a mint at 12:30pm. 30% of students leave early to attend practice for a band concert.
Sample attrition
You measure the level of alertness of a classroom of students. You allow students to choose whether or not they have a mint. You measure their level of alertness again.
N O1 X O2
N O1 O2
You specifically sample students who have the lowest levels of alertness at baseline, and then you randomly assign them to receive or not receive a mint.
Statistical Regression to the Mean
You complete your study on a day following a night of thunderstorms and tornado warnings.
History or timing
You randomly assign students to eat a mint, hold on to a mint, or not have a mint. You measure their level of alertness.
R Xa O1
R Xb O1
R Xc O1
You randomly assign students to receive mints. You find out that some students split their mints in half and gave them to students who were not assigned to receive a mint.
Design Contamination
You conduct your study in a classroom that only includes honors students.
Unique Sample