Download Methods of Research in Psychology

Methods of Research in
Psychology
Some really basic stuff….
• Basic assumptions
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External reality
Time has direction
Causation
The universe operates according to rules
• How do you prove or disprove these?
Assumptions, Laws …
• Law of gravity, of thermodynamics, of
supply and demand
• Laws usually describe an event or process
• Laws have been confirmed so many times
that we always accept them
Theories
• Summarize and organize experience (from
observations and experiments)
• Generate testable predictions (hypotheses)
• Theories
– Are internally consistent
– Are compatible with available evidence
– Are tested over a wide range of evidence
Theories
• Can evolve to incorporate new evidence
• Are neither proven nor disproven – we can
discard them as being no longer useful
Hypotheses, Observations,
Experiments
• Hypotheses are predictions, not descriptions
of reality
• Observations and experiments are subject to
many problems – perception, design,
interpretation
• In science, observations and experiments
must be replicated
Scientific Attitude
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Humility
Skepticism
Creativity
Curiosity
Critical thinking
– Examine assumptions …
Q1
Scientific Method - Q2
What are the elements of the scientific
method?
Q3 - Methods of research
• Longitudinal
– Study the same cohort of HS students from
freshman year to senior year
– How has this group changed in conformity over
four years?
• Cross-sectional
– Study entire HS population at one time
– How do freshmen and seniors differ in
conformity?
Descriptive methods of research
• Case Study – Q4
• Why use a case study?
• Strengths?
• Weaknesses?
Q5 - Descriptive methods
• Naturalistic observations
– Strengths?
– Weaknesses?
• Clinical observations
– Strengths?
– Weaknesses?
Descriptive methods
• Benefits
– Often easy to do
– Provides information, descriptions of behavior
– May suggest ideas for research
• Dangers
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Overconfidence
Hindsight bias
No predictions, no cause & effect
Observer effects - behavior different when watched?
Researcher effects - wording, etc
False consensus
Social desirability bias
Q6 – Research design
• See research design handout
Q7 - Sampling
• Finding a random sample
• Finding a representative sample
• Sampling problems
– Limited population
– Self-identified subjects
Q8 - Confidence levels
• Research usually done to .95
• Determined in part by your sample size
• For more info, take a stats class
Q9 - Correlations
• Identify relationship …
• Variables must be …
– Height in inches OK?
– Male or female OK?
• Relationship
• Predictions?
• Cause and effect?
Correlation coefficients
• Q10 – -1.0 to 0.0
– 0.0 to 0.5
– 0.5 to 1.0
Correlation example
• Students who get more sleep every night do
better in school
Operational definitions – Q11
• “get more sleep” - measure this…
• “do better in school” - measure this…
– Can you use whether or not the student
graduates as a correlation variable?
Operational definitions
• Define the variables so that the research can
be repeated (replicated)
• Op defs must be measurable
• Op defs must be repeatable
• Collect data, probably with a survey
• Why would observations be difficult?
Q12
• Plot your data on a scatterplot graph
• The graph on the next page has a correlation
of .83
hours of sleep vs GPA
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hours of sleep
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GPA
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Best fit - trend - line
• Best fit - trendlines
• http://argyll.epsb.ca/jreed/math9/strand4/scatt
erPlot.htm
• If correlations have predictive value, what
can you predict from this graph?
• Let’s try another
• Number of letters in last name vs height in
inches. Hypothesis: more letters = taller
• What are op defs?
• Dangers of correlational studies?
– False consensus – Q13
– Illusory correlation
– Survey issues
• Sample issues
• Wording effects – Q14
• Researcher effects
Experiments
• Determine cause and effect
• Hypothesis - what is a hypothesis again?
• Subjects should be assigned randomly from
a random and representative sample – Q15
• Independent and dependent variables – Q16
• Operational definitions
• Control and experimental groups – Q17
Let’s do an experiment
• Hypothesis: women who drink a lot of
alcohol in pregnancy will have children
with lower intelligence.
• Where do we start?
• Identify the independent and dependent
variables
• Define the variables operationally
• Do we need control and experimental
groups?
• How do we choose our subjects?
• What sample do we choose our subjects
from?
• Design the experimental procedure
• Q18 – Double-blind / single blind
• What problems are we likely to run into?
Dangers!
• Procedural problems
• Overgeneralization
• Placebo effect
• Experimenter effects
• Ethical problems
Coming up…
• Ethics
• Statistics
General Principles
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Do good
Be responsible
Have integrity
Be just
Be respectful
APA Research Ethics
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Informed consent – Q19
Inducements / force
Pain – Q20
Deception
Debriefing – Q21
Animal care
Fabrication
Plagiarism
IRBs – Q22, Q23
Statistics
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Measures of central tendency
Measures of dispersion
Bell curves and other curves
Graphs
Significance
Q24 - Central tendency
• Mean
• Mode
• Median
Dispersion
• Range
• Variation – average of squared distances
from the mean
• Q25 - Standard deviation - square root of
variation
Range
• The difference between the largest and
smallest data point
• How useful is this?
Variation
• The average of the squared differences of
each data point and the mean
• Why square them?
• Is this useful?
Standard deviation
• The square root of the variation
– N? or N-1? Some thoughts for stats students
• Is this useful?
Normal curve
• Q26 - Or normal distribution, bell curve
• a bell curve
• http://acsweb.fmarion.edu/Pryor/bellcurve.htm
• Do all normal curves look the same?
Skewed distribution
• Q27 - Distribution other than normal
• Skewed distributions
• http://davidmlane.com/hyperstat/A11284.ht
ml
• Do all skewed distribution curves look the
same?
• Positive/negative skew = the tail’s direction
• What’s the mean and standard deviation on
a normal curve?
• Is there a relationship between std dev and
the normal curve?
• Do all normal curves have the same mean
and std dev?
• Do all skewed curves have the same mean
and std dev?
Graphs - displaying data
• Scatterplots and bar graphs more common
in our work
• Many instructive, but silly graphs (PG-13
rated)
• http://graphjam com
Q28 - Within one SD…
• With any standard distribution, the
distribution will always be:
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68% within 1 SD of mean
13.5% between 1 and 2
2% between 2 and 3
99.7% within 3 SD of mean
68 – 95 – 99 rule
Chebychev
• For a non-standard distribution
– 75% with in 2 SD
– 89% with in 3 SD
– What is a z-score?
Q29 - Inferential statistics
• From our statistics, we can make predictions about
the population as a whole.
• How accurate will these predictions be?
• We would apply laws of probability to our data to
determine the accuracy of our predictions essentially we will determine the likelihood that
our results are real or the result of chance.
• For more info, take a stats class…
Q 33 - Statistical significance
• Sample averages are reliable
• Average differences are relatively large
• Low probability that findings are purely the
result of chance
• Then my findings are statistically
significant