experimental designs

Question 1

types of experiments

Answer 1

• lab
• field
• quasi

Question 2

lab experiments

Answer 2

• the IV is manipulated by the researcher and the experiment is carried out in a laboratory or other contrived setting away from the participants’ normal environment

Question 3

advantages of lab experiments

Answer 3

• Good control of extraneous variables.
• Casual relationships can be determined.
• Strict procedures allow them to be replicated, so researchers can be more confident about their findings.

Question 4

disadvantages of lab experiments

Answer 4

• The artificial situation could make participants behaviour unrepresentative.
• Participants could respond to demand characteristics and alter their behaviour.

Question 5

field experiments

Answer 5

• the IV is manipulated by the researcher but this time the experiment is carried out using participants in their normal surroundings

Question 6

advantages of field experiments

Answer 6

• As participants are in their normal situation, their behaviour is likely to be representative.
• Participants could be unaware they are in a study, so demand characteristics are less problematic than in laboratory experiment.

Question 7

disadvantages of field experiments

Answer 7

• Control over extraneous variables is more difficult than in a laboratory, so they are less reliable and replication is more difficult.
• The researchers cannot be sure that changes in the DV have been caused by changes in the IV.
• Ethical issues.

Question 8

quasi experiments

Answer 8

the IV is naturally occurring (e.g. cloudy conditions versus sunny conditions; morning versus afternoon), not manipulated by the researcher

Question 9

advantages of quasi experiments

Answer 9

• they can be used to study real world issues. - If participants are in their normal situations their behaviour is likely to be representative.
• If participants are unaware they are in a study, demand characteristics will be less problematic. - They enable researchers to investigate variables that could not practically or ethically be manipulated.

Question 10

disadvantages of quasi experiments

Answer 10

• They are only possible when naturally occurring differences arise.
• Control over extraneous variables if often very difficult.
• As the researcher is not manipulating the IV, they can be less sure of the cause of changes in the DV, e.g. a casual relationship cannot be established.

Question 11

experimental designs

Answer 11

• repeated measures
• independent measures
• matched groups design

Question 12

repeated measures design

Answer 12

this involves using the same people in each condition

Question 13

advantages of repeated measure design

Answer 13

• Individual differences are unlikely to distort the effect of the IV, as the participants do both levels. - Counterbalancing reduces order effects.
• Uses fewer participants so is good when participants are hard to find.
• Blind procedures can reduce demand characteristics.

Question 14

disadvantages of repeated measures

Answer 14

• Order effects such as practice and fatigue and other extraneous variables could distort the results. - Participants see the experimental task more than once, increasing the risk of demand characteristics.

Question 15

independent measures design

Answer 15

this involves using different people in each condition

Question 16

advantages of independent measures design

Answer 16

• Different participants are used in each level of the IV so there are no order effects.
• Participants see the experimental task only once, reducing the risk of demand characteristics.
• Effects of individual differences reduced by random allocation to levels of IV.

Question 17

disadvantages of independent measure design

Answer 17

• Individual differences could distort results if participants in one level of IV differ from those in another.
• More participants are needed than with repeated measures design, which may be less ethical or harder to find.

Question 18

matched groups design

Answer 18

involves using different people in each condition but an attempt is made to make the participants as similar as possible on certain key characteristics (any that might influence the findings).
- This is done by testing the individuals on the key characteristics, pairing them based on similar scores, and then placing one member of each pair into each group.

Question 19

advantages of matched groups design

Answer 19

• Participants see the task once, reducing the risk of demand characteristics.
• No order effects.
  -Controls for individual differences.

Question 20

disadvantages of matched groups design

Answer 20

• Similarities between pairs is limited and may be flawed if important variables for matching are unknown.
• Time consuming and difficult.

Question 21

type of extraneous variables

Answer 21

• participant variables
• situational variables;
  > order effects
  > environmental factors
  > demand characteristics

Question 22

participant variables

Answer 22

• examples; Age, intelligence, motivation, skill, experience, gender.
• how they are controlled;
  > same people in each condition (repeated measures design) or extremely similar people in each condition (a matched groups design).
• If using an independent groups design, allocates participants to conditions on a random basis so that participant variables are more likely to be evenly distributed between conditions.

Question 23

situational factor - order effects

Answer 23

• examples; If doing the same activity twice, participants may do better the second time because of practice or worse because of boredom.
• how they are controlled;
  > Having different people in each condition will avoid this problem, which would be a benefit of using either an independent measures design or a matched pairs design.
  > If a repeated measures design is used, then this should be counter-balanced. This is where the participants are split into two groups: group 1 does condition 1 first then condition 2, while group 2 does condition 2 first then condition 1.

Question 24

situational factor - environmental factors

Answer 24

• examples; such as time of day, temperature and noise
• how they are controlled;
  > impose controls on the experiment to ensure that there are as few differences as possible between the two conditions (e.g. do both conditions in the same room, with the same temperature levels, same colour walls, same light levels, etc.).

Question 25

situational factor - demand characteristics

Answer 25

• examples; these are cues in an experiment that communicate to participants what is expected of them and which may unconsciously affect the behaviour of participants.
• how they are controlled;
  > Do not tell participants the aim of the investigation. (This is known as a single blind procedure)

Question 26

researcher bias

Answer 26

• term used to describe effects of a researcher’s expectations on a participant’s behaviour.
• To control for this, standardised instructions should be used to ensure the experimenter says the same things to each participant and to prevent any hints from being given. If the participant can be left uncertain as to what the precise aim of the research is, this is known as single blind.