Quasi experiments

Question 1

What is a quasi experiment?

Answer 1

• a quasi experiment is not a ‘true’ experiment because the independent variable (IV) is not deliberately manipulated.
• this means that it is not possible to claim that changes in the dependent variable (DV) are caused by the independent variable.
• however in some circumstances, a quasi experiment is the only way to study behaviour.

Question 2

What are the two different types of quasi experiments?

Answer 2

• those with an IV (natural experiments) and those with no IV (difference studies)

Question 3

What are natural experiments?

Answer 3

• a natural experiment is conducted when it is not possible, for ethical or practical reasons, to deliberately manipulate an IV. Therefore it is said that the IV ‘varies’ naturally and thus the term ‘natural experiment is used’
• the DV may be tested in a laboratory.
  e. g.; Berkowitz (1970) compiled monthly FBI crime statistics on the frequency of violent crimes from january 1960 to december 1966. he reported a steep increase in the number of violent crimes being recorded following november 1963. this, he proposed, was the result of the american population being exposed to television footage of kennedy’s assassination.
• in this example, the IV was not controlled by the researchers, they took advantage of something which would be practically and ethically quite difficult to control.

Question 4

What are difference studies?

Answer 4

• in a difference study the apparent IV is also naturaly occurring and the DV may be measured in a laboratory.
• The key feature is that the IV has not been made to vary by anyone. It is simply a difference between people that exists. so it isn’t actually a variable at all.
• Sheridan and king (1972) tested obedience by asking male participants to give genuine electric shocks of increasing advantage to a puppy. They found that 54% of male participants delivered the maximum (non fatal) shock, but the obedience rate for females was a staggering 100%. The IV in this study was gender - a difference that cannot be manipulated and thus not a true IV
• in this example the characteristics of people, gender or visual ability, is being investigated and hence is the IV of the research.

Question 5

Evaluate manipulation of the IV?

Answer 5

• the lack of control over the IV means that we cannot say for certain that any change in the DV was caused by the IV.
• for example, if there were uncontrolled confoudning variables then observed changes in the DV might not be due to the IV.

Question 6

Evaluate random allocation

Answer 6

• in an experiment with an independent groups design participants are randomly allocated to conditions. this is not possible in natural or quasi experiments. this means that there may be biases in the different groups of participants
• this means that, due to the lack of random allocation, there may be uncontrolled confounding variables.

Question 7

evaluate unique characteristics of participants?

Answer 7

• the sample studied may have unique characteristics. the unique characteristics of the sample mean that the findings can’t be generalised to other groups of people (i.e the study may be described as having low population validity