Extraneous Variables + Standardization of procedures and instructions

Independant Variable

An IV is purposefully manipulated by the experimenter to see if it has an effect on the dependant variable. The IV is the condition that is given to the experimental group, and the placebo (fake treatment) is given to the control condition

Dependant Variable

o   This is the variable that is measured

o   The experimenter manipulates the IV to see if it has a cause-effect on the DV

Control Variable

o   Is any variable that is constant in research conditions

(e.g. the researcher may control that each participant gets 50g of coffee or control the types of food consumed, and the amount of time before one goes to sleep)

o   they do this to make the conditions as similar as they can be

(e.g. WACE Exam, NAPLAN)

Extraneous Variables

o   is a variable other than the IV that may cause a change in the DV, and therefore have an unwanted effect on the results of the experiment

o   it is not intentionally studied by the experimenter, but they can make it difficult to conclude with confidence that any change in the DV was caused solely by the presence of the IV

o   So the experimenter will try and identify all relevant extraneous variables when designing their experiment, and will try to monitor and control their influence by using procedures that will minimize the extraneous variable
(e.g. random allocation of participants, single-blind and double-blind procedures, and standardization of procedures and instructions)

Types of Extraneous Variables

1. Participant Variables

2. Environmental Variables

3. Research Variables

4. Confounding Variables

Participant Variables

These are the personal characteristics that individuals participants bring to an experiment, and which influence their responses

These may be biological, psychological and/or social in nature. The experimenter will try to ensure that these minimized or controlled before the experiment commences

 These all affect how participants behave in an experiment and therefore the results including generalisations that may be made

e.g. being more anxious, mental abilities, intelligence, learning, memory, reading comprehension, problem-solving skills, physical strength, hearing, sight, age, diet, medication, education, ethnicity, religious beliefs, mood etc ect

Environmental Variables

Environmental variables occur outside the individual and they are external factors (other than the IV) associated with the experimental setting which may influence the participant responses and therefore the results

e.g. background noise, lighting conditions, temperature, time of the day, presence of other participants, room etc.

Research Variables

These are the variables that relate the experimenter and how they affect the participants and therefore the results (experimenter effect)

• Personal characteristics of the experimenter may contribute to the experimenter effect including their age, sex, ethnicity, cultural background, accent, attitudes, biases and expectations

The way the experimenter treats participants differently depending on whether they are in a control or experimental group which will influence the behaviour of the participants

if the experimenter is tired, or in a bad mood....same thing

• Experimenter expectancy these are the cues the experimenter provides about the responses a participant should make e.g. body language (facial expression, mannerisms and tone of voice)

 

unintentional errors, when they make mistakes in analysing and interpreting results.

Confounding Variables

A confounding variable is any variable other than the IV and HAS HAD AN EFFECT ON THE DV. It can NOT be separated from that of the IV. It is not controlled or manipulated by the researcher. It has an effect of the SAME time or together with the IV, so the experimenter cannot tell which of the variable produced the change in the DV

 

It is like a second unwanted IV that effect the DV and therefore the results

It’s called a confounding variable because its effects are “CONFUSED” with those of the IV

An experiment with one or more confounding variables compromises the interpretation of the results and the validity - specifically internal validity

Demand Characteristics

When people know they are in an experiment, they may behave in ways that they think the experimenter wants them to. Demand characteristics are cues in an experiment that may influence or bias a participant’s response, thereby distorting the results.

 

Demand characteristics are NOT their true responses – these may be intentionally or subconsciously

Experimenter Effects

The experimenter effect refers to any influence the experimenter (or any other researcher) may have on the results of their investigation. This influence may have occurred through interaction with the participants or unintentional errors when making observations, measuring responses or when analyzing/interpreting results

 

also known as experimenter bias or research bias

3 features of Experimenter Effect

Personal characteristics of the experimenter may contribute to the experimenter effect including their age, sex, ethnicity, cultural background, accent, attitudes, biases and expectations

The way the experimenter treats participants differently depending on whether they are in a control or experimental group which will influence the behavior of the participants

If the experimenter is tired, or in a bad mood … same thing

 

Experimenter expectancy – these are the cues the experimenter provides about the responses a participant should make e.g body language (facial expressions, mannerisms and tone of voice)

 

Unintentional errors - when they make mistakes in analyzing and interpreting results

Placebo Effect

The placebo effect refers to a change in behaviour, symptoms, or physiological responses that occurs because a participant believes they are receiving an active treatment, even though they are actually receiving a placebo (an inactive substance or procedure that has no therapeutic effect).

Why does the placebo effect happen, what are the 4 main ideas?

1.        Expectancy effects

2.        Classical conditioning

3.        Demand characteristics

4.        Cognitive reinterpretation

Expectancy Effect in Placebo Effect

Participants expect improvement, so they unconsciously change their behaviour or perception.

Classical Conditioning in Placebo Effect

Past experience with real treatments leads the body to produce a similar response when given a placebo.

Demand Characteristics

Participants act in ways they think the researcher wants.

Cognitive Reinterpretation

Participants reinterpret symptoms (“I think my pain is better”) because they believe treatment is helping.

What are the steps to minimise extraneous and confounding variables?

1. Random Allocation

2. Single-Blind Procedures

3. Double-Blind Procedures

4. Use of Placebo

Random Allocation (minimising extraneous variables)

Random allocation is a crucial feature of any controlled experiment so that any differences found between groups or conditions can confidently be attributed to the effects of the IV. With a sufficiently large number of participants, it is reasonable to assume that each group will end up the same kind of spread of participant characteristics that may affect the DV and therefore the results.

Single-Blind Procedures (minimising extraneous variables)

When the participant does not know whether they have been exposed to the experimental (given the IV) or control group (not given the IV), but the experimenter does know. Placebos are used in this instance

advantage of single-blind procedures (minimising extraneous variables)

reduces the impact of participant expectations (demand characteristics)

disadvantage of single-blind procedures (minimising extraneous variables)

because the experimenter knows who is in each group they may behave differently towards the different groups (body language, verbal cues, and preferential treatment). Remember Demand characteristics? When the experimenter’s behavior causes a demand for participants to perform as the experiment predicts they will.

Double-Blind Procedure (minimising extraneous variables)

Neither the participants nor the experimenter knows who has been assigned to the experimental and control conditions. It involves a third party knowing which group has been assigned to each of the above groups, but this person is not directly involved with the study.

Advantages of Double-Blind Procedures

eliminates the experimenter effect and demand characteristics

How does use of Placebo minimise the effects of extraneous and confounding variables

1. Both groups experience the same expectations of receiving a treatment.

◦       If both the experimental group (real drug) and control group (placebo) take what appears to be an identical pill, then their expectations about improvement are similar.

◦       This means any expectancy-based changes affect both groups equally.

 

2. Equal expectations reduce unwanted variability.

◦       Expectancy effects no longer influence the DV differently across groups.

◦       This minimises the impact of the placebo effect as an extraneous variable.

 

Standardisation of procedures and instructions + example

The use of standardised instructions means that the instructions given to all participants for each condition should be predetermined and identical in terms of what they state and how they are administered(given). Standardisation means keeping everything the same for all participants so that the investigation is fair.

 

For example, consider the instructions that are given to the participants. In order to ensure that all of the participants get precisely the same instructions. He or she should then either read them to the participants or ask the participants to read them to themselves. This makes sure that the experiment is fair, and we can be sure that the IV is the variable that has affected the DV (and not a confounding variable). 

(Standardisation of procedures and instructions) To ensure that all participants have the same experience, researchers should ensure that they are all tested:

• In the same place, with the same equipment and materials placed in the same way.

 

 • Under the same conditions, so the level of lighting, noise and heat remains the same for all participants.

 

• At roughly the same time of day, as people may behave differently if tested at nine o'clock in the morning rather than five o'clock at night.

 

• Given identical standardised instructions in exactly the same way.

e.g WACE and NAPLAN instructions