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Methods of Research in Psychology Some really basic stuff…. • Basic assumptions – – – – 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 • • • • • 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 – – – – – – – 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 10 9 hours of sleep 8 7 6 5 4 3 2 1 0 0 1 2 3 GPA 4 5 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 • • • • • Do good Be responsible Have integrity Be just Be respectful APA Research Ethics • • • • • • • • • Informed consent – Q19 Inducements / force Pain – Q20 Deception Debriefing – Q21 Animal care Fabrication Plagiarism IRBs – Q22, Q23 Statistics • • • • • 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: – – – – – 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