Research Methods in Psychology Strategies Statistics & Ethics

Research Strategies

Experiment – Researcher changes one or more factors to observe their effect on some behavior or mental process ⁺DOES IDENTIFY CAUSE/EFFECT RELATIONSHIP ⁻Sampling errors, placebo effect, not natural environment could alter true effect

Research Strategies Case Study (descriptive) – in depth fact finding on a single subject ⁺Intensive, specific info ⁻No cause/effect; lots of time; no generalization Naturalistic Observation (descriptive) – Observation in natural/real setting without changing environment ⁺Gathers naturally occurring data; real world ⁻Observer bias; no cause/effect

Research Strategies Survey Research (descriptive) – Collect data through interviews questionnaires {but beware of:} – false consensus effect – bad sampling (especially self-selection!!!) Reduces validity and reliability = wording effects

Research Strategies Correlational studies (descriptive) – Examines the degree* of relationship between two variables ⁺Study real world connections ⁻NO cause/effect just CONNECTION – *”degree of relationship” just means how much they correlate.

Research Strategies One last note about correlational studies: If you HAVE to get a tattoo, then I suggest the following: “Correlation is not causation.”

Research Strategies If marbles of two colors are mixed well in the large jar, the fastest way to know their ratio is to blindly transfer a few into a smaller one and count them

Research Strategies Population – all the cases in a group, from which samples may be drawn for a study Random Sample – a sample that fairly represents a population because each member has an equal chance of inclusion Stratified random samples

Experiments (cont…) Three Possible Cause-Effect Relationships (1) Low self-esteem Depression (2) Depression Low self-esteem Depression (3) Distressing events or biological predisposition could cause or and

Controls Single & Double-blind Procedures – Subjects (or both the subjects and the research staff )are ignorant (blind) about whether the subject has received the treatment or a placebo – commonly used in drug-evaluation studies Placebo – an inert substance or condition that may be administered instead of a presumed active agent, such as a drug, to see if it triggers the effects believed to characterize the active agent

Controls Random Assignment – assigning subjects to experimental and control conditions by chance – minimizes pre-existing differences between those assigned to the different groups

Controls Experimental Condition – the condition of an experiment that exposes subjects to the treatment, that is, to one version of the independent variable Control Condition – the condition of an experiment that contrasts with the experimental treatment – serves as a comparison for evaluating the effect of the treatment

Controls Independent Variable – the hypothesized cause of a phenomenon – typically manipulated by experimenter Dependent Variable – the hypothesized effect in a phenomenon – in psychology it is usually a behavior or mental process – measured by the experimenter

Controls So how do you control for the big daddy of confounds, Chance? – Random assignment to conditions PLUS – Inferential statistics

Research Strategies Comparing Research Methods Research Method Basic Purpose How Conducted What is Manipulated Descriptive - To observe and Case studies, surveys, Nothing One variable at record behavior and naturalistic a time observations Descriptive - To detect naturally Computing correlationsNothing Two variables occuring relationship, sometimes at a time to assess how wellamong survey one variable predictsresponses Experimental To explore causeManipulating one orIndependent and effectmore factors and usingvariable(s) random assignment to eliminate preexisting differences among subjects

Statistics Statistics come in two basic flavors: – Descriptive (duh.) – Inferential : did my observed result REALLY happen, or was it just by chance? Descriptive stats tell you 3 basic things: 1.Central tendency 2.Variability 3.Correlation

Mode – the most frequently occurring score in a distribution Mean – the arithmetic average of a distribution – obtained by adding the scores and then dividing by the number of scores Median – the middle score in a distribution – half the scores are above it and half are below it Mathematical Tools -- Central Tendency --

Range – the difference between the highest and lowest scores in a distribution Standard Deviation – a computed measure of how much scores vary around the mean Statistical Significance – a statistical statement of how likely it is that an obtained result occurred by chance Mathematical Tools -- Variation --

Mathematical Tools -- Covariation -- Correlation Coefficient – a statistical measure of the extent to which two factors vary together and thus how well either factor predicts the other Correlation coefficient Indicates direction of relationship (positive or negative) Indicates strength of relationship (0.00 to 1.00) r = +.37

Mathematical Tools Height and Temperament of 20 Men Subject Height in Inches Temperament Subject Height in Inches Temperament

Mathematical Tools aka Statistical Reasoning Scatterplot – a graphed cluster of dots, each of which represents the values of two variables – the slope of the points suggests the direction of the relationship – the amount of scatter suggests the strength of the correlation little scatter indicates high correlation – also called a scattergram or scatter diagram

Mathematical Tools Scatterplot of Height and Temperament Temperament scores Height in inches

Mathematical Tools Perfect positive correlation (+1.00) No relationship (0.00)Perfect negative correlation (-1.00)

Mathematical Tools: Inferential statistics SOLE purpose: is this result due to chance or not? – Typically assessed with a “probability value” or “p- value” – Cut off is usually.05 (but there’s nothing magical about that number!) – P-values are NOT measures of “effect size” – Effect size is always more important.

Statistical traps… Mistaking correlation for causation – the perception of a relationship where none exists – (re: availability)

Statistical traps… Random Sequences Your chances of being dealt either of these hands is precisely the same: 1 in 2,598,960.

Statistical traps… Cheating with graphs: Our Brand Brand Brand Brand X Y Z 100% Percentage still functioning after 10 years Brand of truck

Statistical traps… Cheating with graphs Our Brand Brand Brand Brand X Y Z 100% Percentage still functioning after 10 years Brand of truck

Statistical traps… Which mean is which? A Skewed Distribution Mode Median Mean One Family Income per family in thousands of dollars

World’s fastest ethics lecture Doing research with humans – basic principles: – Rights & well-being of participants outweigh the benefits of the research – Participants have to be allowed to decide to participate or not: Informed Consent is the cornerstone of ethical research.

World’s fastest ethics lecture – Participants have the right to withdraw from the study at any time, without penalty. – Participants must be protected from risks or informed of risks that can’t be removed. Risk/benefit ratio must be positive. – Deception is avoided whenever possible and must be justified if it is used.

World’s fastest ethics lecture – Researchers have the duty to inform the participants of the true purpose of the study (usually done in the debriefing) – Data must remain confidential and secure (trickier these days with computers!)