Experimental methods

1. Experimental Methods

2. Experiments in Psychology
 One of the most widely used methods in the study of behavior
 Goal is to establish a cause and effect relationship between two
variables
 Performed under highly controlled conditions
 Experiment is an example of quantitative research – it generates
numerical data
 Can be statistically tested to rule out the role of chance in results

3. Does noise affect one’s ability
to recall information?
• Aim of study – will one variable (noise) has an effect
on another variable (recall or information)
• Independent Variable (IV) – causes a change in
another variable, it is manipulated by researcher
• Dependent Variable (DV) – variable that is
measured after the manipulation of the IV

4. Operationalizing Variables
• The experiment must be written in a way that it is
clear WHAT is being measured. Here, noise is the
independent variable
– It could be operationalized as high music at
volume 35
• The number of words remembered would be the DV
– It could be operationalized as words remembered
from a list of 20 words

5. Apply your Knowledge
 Operationalize your variables by considering each of the following
descriptions and deciding whether it is an example of aggression or not.
 Write a well-worded definition of aggression.
1. Two men fight over a parking place
2. A football player kicks the ball into the goal
3. Two girls give a boy the “silent treatment” on the playground
4. A man kicks the back of his car when it will not start
5. Three students have a heated debate about whether global warming is
happening

6. Formalize the aim –
Researcher forms an experimental hypothesis
• Researcher predicts the relationship between the IV and the
DV – what we expect will come out of the manipulation of IV
• In this case there will be 2 conditions:
– Participants recall words in the quiet
– Participants recall words with loud noise
the quiet condition is called the CONTROL CONDITION
so that we can see if there is a difference

7. Make up an experimental hypothesis
for this study

8. How About
Noise will decrease the number of words that an
individual is able to recall from a list of words.
The IV (noise) is predicted to have an effect on the
DV (recall)

9. More Kinds of Hypothesis
• In Experimental Research you need a NULL
HYPOTHESIS and an EXPERIMENTAL HYPOTHESIS
• A null hypothesis: Noise has no effect on an
individual’s ability to recall a list of words
• Remember, you can never prove anything! You can
only disprove.

10. A researchers goal:
• Refute the null hypothesis (that sound makes no
difference in recall)
• Or accept the null hypothesis
• We can accept the experimental hypothesis only
if we demonstrate the effect was due to the
manipulation of the IV

11. Identify the IV and DV in each of the experimental hypothesis:
1. People are more likely to make a risky decision
when they are in a group than when they are alone.
2. An increase in carbohydrates decreases one’s ability
to concentrate.
3. People will react more quickly to an auditory
stimulus than a visual stimulus.
4. Lack of sleep will affect learning new words
negatively.

12. Kinds of Experiments
• Laboratory
– Strict control of variables, easy to replicate
– Artificial environment, participants may react differently than
real life (ecological validity?)
• Field
– Natural environment (ecological validity) but can’t control all
variables
• Natural
– Researchers have no control over variables.
– Naturally occurring, researchers are there to study

13. Biases on experiments
Demand characteristics is a subtle cue that makes participants aware
of what the experimenter expects to find or how participants are
expected to behave. Demand characteristics can change the outcome
of an experiment because participants will often alter their behavior
to conform to the experimenters expectations. use single
blind control)
• The Hawthorne effect is a term referring to the tendency of some
people to work harder and perform better when they are participants
in an experiment. Individuals may change their behavior due to the
attention they are receiving from researchers rather than because of
any manipulation of independent variables.

14. Biases in experiments
• Researcher bias – researcher sees what he is looking for
• Experimenter expectancy – tendency for experimeter`s
knowledge of what is being tested to influence the outcome of
reserach use double blind control
• Confounding/ extranous Variables – anything other than the
independent variable thatcould affect the dependent variable
• Participant variability use random samples
• Ecological validity – the extent to which reserach can be
generalised to other places or conditions

15. Correlational studies
are used to look for relationships between variables.
There are three possible results of a correlational study:
1. a positive correlation,
2. a negative correlation, and
3. no correlation.
• The correlation coefficient is a measure of correlation strength
and can range from –1.00 to +1.00.
• There is no CAUSE-and-EFFECT relationship.
• http://tylervigen.com/