Transcript Psychological Research Methods

Psychological Research
Methods & Statistics
Excavating Human Behaviors
Psychology & Research Methods
A “Scientific Attitude” is critical…
Curiosity – a passion to explore and understand.
 Skepticism – psychologists, like other scientists,
approach the world of behavior with curious doubt.
They are constantly asking two questions: What does it
mean? How do you know?
 Humility – an awareness and acceptance that we may
have to reject our own ideas or theories (if they are
proven wrong).
 Critical Thinking – a scientific approach
prepares/demands us to think “smarter”  to examine
assumptions, evaluate evidence, and assess conclusions.
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Hindsight Bias
The tendency to
believe, after learning
the outcome, that you
knew it all along.
 With 20/20
hindsight, everything
seems obvious.
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Overconfidence
We tend to think we know more
than we do.
 We tend to be more confident than
correct!
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82% of U.S. drivers consider themselves to
be in the top 30% of their group in terms
of safety
81% of new business owners felt they had
an excellent chance of their businesses
succeeding. When asked about the success
of their peers, the answer was only 39%.
(Now that's overconfidence!!!)
Exercise: Unscramble these Anagrams
WREAT
ETRYN
GRABE
Anagram Solutions
WREAT
--- WATER
ETRYN --- ENTRY
GRABE --- BARGE
Psychological Research Methods
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Psychology is an experimental science.
Assumptions must be supported by evidence.
Psychologists use a variety of research methods
to study behavior and mental processes.
Psychologists follow the same general procedure
when conducting research:
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Asking research questions
Forming hypothesis (hypotheses)
Testing the hypotheses
Analyzing the data (results)
And drawing conclusions
Eventually, replicating research
The Scientific Method
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Step 1: Forming research questions –
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Beginning with scientific curiosity and interest, many
research questions come from daily experience, psychological
theory, or common knowledge.
Step 2: Forming hypotheses –
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An hypothesis is a statement of that which you wish to prove.
An hypothesis is a predicted “answer” to the question (or in
the words of some researchers, “an educated guess”).
The Scientific Method
 Step 3: Testing hypotheses –
1. Once a hypothesis has been formed, it must be scientifically
tested and proved right or wrong.
2. This part of conducting research is the “actual” experiment.
3. Psychologists use a variety of methods to test hypotheses.
 Step 4: Analyzing Results –
1. Data is analyzed using statistics.
2. The more data collected,
the more complex a task
it is to analyze.
The Scientific Method
• Step 5: Drawing Conclusions –
• Once the results have been analyzed, a psychologist can
draw or make conclusions about his/her questions and
hypotheses.
• Step 6: Replication –
1. Even when a research study carefully follows proper
procedures, its findings might just represent a random
occurrence.
2. To confirm the results and conclusions of a research study,
the study must be replicated.
3. The study must be repeated and it must produce the same
or similar results as before.
4. If there are different results, then the findings of the first
study are questioned.
Selecting Subjects
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Population – all members of a given group
(within the study).
Sample – a subset of the population which
is representative of the whole population.
Random Sample – a sample in which every
member of the population has an equal
chance of being selected.
Stratified Sample – a sample in which each
subgroup of the population is represented
proportionally to its size in the population.
Key Research Terminology
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Using a random sample that represents the
whole population, a researcher can
generalize findings to the entire population.
CAUTION: Overgeneralization – is the
making of generalizations using
unrepresentative cases. It is easy to do but
typically erroneous.
False Consensus Effect: the tendency to
overestimate the extent to which others
share our beliefs and behaviors
Methods of Collecting Data
Survey – commonly used in both descriptive and
correlational studies, questionnaire method
sampling many cases (individuals) in less depth
 Case Study – the study of one or more individuals
in great depth, to inform about an entire
population or sample
 Testing – psychological tests are given to measure
certain mental processes, such as intelligence,
aptitude, or personality
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The Survey Method
 Used
in both descriptional and
correlational research.
 Use Interview, mail, phone, internet
etc…
 The Good- cheap, anonymous, diverse
population, and easy to get random
sampling (a sampling that represents
your population you want to study)
Survey Method: The Bad
 Low
Response
Rate
 People Lie or
just
misinterpret
themselves.
 Wording
Effects
How accurate would a
survey be about the
frequency of diarrhea?
Naturalistic Observation
Observing and recording
behaviors of an organism
in natural environment
 No control- just an
observer
 This method does not
explain behavior but
describes it
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What are the benefits and detriments of
Naturalistic Observation?
Methods of Collecting Data
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Laboratory Observation – this research method
involves watching and recording behaviors of
organisms NOT in their natural environment BUT
in a laboratory setting.
Cross-sectional Studies – uses participants (subjects)
of different ages to compare how certain variables
may change over the life span.
Longitudinal Studies – use one group of
participants over a long period of time. This
method of study tracks the change over time of the
participants.
Correlational Research
 Detects
relationships between variables
 Does NOT say that one variable causes
another
There is a positive
correlation between ice
cream and murder
rates. Does that mean
that ice cream causes
murder?
Correlation vs. Cause & Effect
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Correlation coefficient is a statistical
measure of relationship (it reveals how
closely related two factors are or how
closely two factors vary together and thus
how well either one predicts the other).
Positive and negative correlations are
possible
A relationship does not mean causation!!!
• For example, watching TV violence positively
correlates with aggressive behavior; but does
not necessarily mean watching violence on TV
causes aggressive behavior.
How to Read a Correlation
Coefficient
Experimental Research
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Explores cause and effect relationships
Eating too many bananas causes
Constipation
Experimental Research
In an experiment, participants receive
what is called a treatment, such as a
change in room temperature or a new
drug.
 Then, psychologists carefully observe
the participants to determine how the
treatment influences their behavior.
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Independent and Dependent
Variables
All research studies measure and
observe variables (factors), especially
experimental studies.
 In an experiment, the independent
variable is the factor that the
researcher manipulates (controls) so
that they can determine its effect on
the dependent variable.
 The dependent variable is the factor
that depends on the manipulated
independent variable(s).
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Experimental and Control Groups
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The experimental group is a group of participants who
receive the treatment or manipulated variable.
The control group is a group of participants who do not
receive the manipulated variable (instead a placebo of
sorts).
All other variables/factors are held constant (or equal)
for both groups (to try to isolate a cause and effect
relationship between independent variable(s) of interest
to the research psychologist and the dependent variable.
If the research psychologist fails to manage the ‘other’
variables (or hold them constant), they become
confounding variables. Confounding variables are
baaaaad!!!
Experimental Method
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continued
Psychologists randomly place participants (subjects) into
one group or another.
– EXAMPLE: The effect of extracurricular activities on student’s
academic success.
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Once subjects are randomly placed into the control and
experimental groups, the researcher makes sure that all
other variables are the same for all students regardless of
group.
Using this grouping method in the experimental method is
called a controlled experiment.
The Placebo Effect
 In research studies and in our daily lives, our expectations
affect what happens to us.
 Feeling better simply because we expect to feel better
and for no other reason is an example of the placebo
effect.
 A placebo is a substance or treatment that has no effect
apart from the person’s belief in it.
Experimental Method
continued
Single-blind vs. Double-blind Studies
 In a single-blind study, participants do not
know whether they are receiving the
treatment (the manipulated independent
variable) or not. In other words, they do not
know if they are in the experimental group or
in the control group.
 This process avoids the placebo effect.
 In a double-blind study, both participants
and researchers are unaware of who has
placed in which group.
Statistics & Research Methods
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Describing (Quantifying) Data
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Scaling – assigning numbers to observed events
(responses, etc.)
Categorical Scale (Nominal) – a number/score is
assigned to individuals so as to group responses into
categories (example: gender)
Ordinal Scale – assigning numbers to convey relative
meaning among responses (example: making a list from
“most” to “least”
Interval Scale – assigning numbers/scores in which
equal differences can be treated as equal units
(example: reaction time)
Ratio Scale – relative scores assigned by way of
multiples and includes a true zero point (example: 15 is
3 times greater than 5)
Statistics & Research Methods
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Frequency Distribution – a set of data that tells you how many…
Descriptive Statistics
Measures of Central Tendency
 Mark the center of a distribution  Mean, Median, Mode
 Mean – is average of all the scores in a distribution
 Median – is the central score in a distribution
 Mode – is the score that appears most frequently
 The mean is the most commonly used measure of central tendency, but its accuracy
can be distorted by extreme scores or outliers.
Measures of Variability
 Range – is the distance between the highest and lowest scores in a distribution.
 Variance – is the amount of difference/variability between scores in a distribution.
 Standard deviation – is simply the square root of the variance (Both variance and
standard deviation relate the average distance of any score in the distribution from the
mean).
 Z-scores – measure the distance of a score from the mean in units of standard
deviation (to compare scores from different distributions).
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Normal Distribution or Normal Curve or Bell-shaped Curve – approx. 68% of
scores in a normal distribution fall within one standard deviation of the mean and
approx. 95% of scores fall within two standard deviation of the mean.
Statistics & Research Methods
Inferential Statistics
 While descriptive statistics provide a way to summarize information about
a sample studied, the purpose of inferential statistics is to determine
whether or not findings can be applied to the larger population from which
the sample was selected.
 The extent to which the sample differs from the population is known as
sampling error.
 A few inferential statistical tests exist such as t-tests, ANOVAs, and
MANOVAs.
 These tests take into account both the magnitude of the difference found
and the size of the sample.
 All these tests yield a p value. The smaller the p value, the more significant
the results.
 P value of .05 is the cutoff for statistically significant results. (p value of
.05 means that a 5% chance exists that the results occurred by chance.
 P value of .01 is sometimes sought for greater certainty of significant
results.
 P value can never equal 0 because one can never be 100% certain that
results did not happen randomly by chance.
 Replication allows for greater certainty of results.
Statistics & Research Methods
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Null hypothesis: (H0) is a hypothesis (scenario)
set up to be nullified, refuted, or rejected
('disproved' statistically) in order to support an
alternative hypothesis
Type I error: the error of rejecting a null
hypothesis when it is actually true
Type II error: the error of failing to reject a null
hypothesis when the alternative hypothesis is the
true state of nature
T-test
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The t-test assesses whether the means of two
groups are statistically different from each other.
This analysis is appropriate whenever you want
to compare the means of two groups
www.graphpad.com/quickcalcs/ttest1.cfm
X = mean of group
Var = Standard deviation of group
N = number in sample
Research & Statistics Assignment 1
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Gather shoe size data from 10 females and 10
males, recording the shoe size of each.
Then calculate the measures of central tendency
(mean, mode, median) and graph the data set in
a frequency histogram and box-plot.
Find and discuss any outliers
Explain the gender difference, if one exists.
Research & Statistics Assignment 2
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Using the Research Question: How many pairs of
shoes do males and females own? Write a testable
hypothesis.
Next, gather data from 10 females and 10 males,
recording the number of shoes owned by each.
Ask your participants, “How many pairs of shoes do
you own?” and (obviously) record their answer and
gender.
Calculate the measures of central tendency and
standard deviation and test for differences between
means using a t-test. (use
www.graphpad.com/quickcalcs/ttest1.cfm to help you
calculate a t-score)
Write a brief conclusion about your results (at least 1
paragraph). Make sure you give an explanation for the