Descriptive Methods & Experimentation

Descriptive Methods •

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Summary: Case studies, surveys, and naturalistic observation describe behaviors. Correlation: Correlation: when one trait or behavior accompanies another, we sat that the two correlate. o + means that they both go up or down together – means that they go opposite ways (one up/one down) o Scatterplots: a graph comprised o points that are generated by values o two variables. !he slope o the points depict the direction "erect "erect negative# $%.&& o "erect "erect positive# +%.&& o o 'o correlation# &.&& Correlation Correlation and Causation: correlation does not mean causation  ust because two things go together, does not mean mean that one can ma*e a conclusion and guess about two things that correlate because it not always is true that they will cause each other to do things. llusory Correlation: Correlation: the perception perception o a relationship where no relationship actually eists. "arents conceive children ater adoption. o -rder in andom events: given random data, we loo* or order and meaningul patterns o "o*er "o*er hand that is dealt (royal hand is ust as li*ely as random number hand) Someone wining the lottery twice on the same day da y o

Experimentation : eploring cause and e0ect •

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1periments manipulate actors that interest us while other actors are *ept under control 2ouble 3lind procedure: when a doctor and a patient both do not *now i the drug administered is a placebo or not andom 4ssignment: assigning participants to eperimental eperimental (breast$ed) and control (ormula$ed) conditions by random assignment minimi5es pre$eisting pre$eisting di0erences between the two groups ndependent 6ariable: a actor manipulated by the eperimenter.  !he e0ect o the independent independent variable is the ocus o the study. study. 1: when eamining the e0ects o breast eeing upon o intelligence. ntelligence is the dependent variable

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Statistical reasoning: statistical procedures analy5e and interpret data allowing us to see what the unaided eye misses. 2escribing 2ata: a meaningul description o data is important in research. 7isrepresentation may lead to incorrect conclusions. 7easures o Central !endency: 7ode: the most re8uent number in a set o 7ean: the average o the numbers in a set o o 7edian: the middle score in a ran*$ordered set 7easures o 6ariation o ange: the di0erence between the highest and the lowest scores in a distribution Standard deviation: a computed measure o how much o scores vary around the mean. llusion o Control: the chance events are subect to personal control is an illusion o control ed by$ llusory correlation: the perception o a relationship where o no relationship actually eists o egression towards the mean: the tendency or etremes o unusual scores 7a*ing inerences: a statistical statement o how re8uently an obtained result occurred by eperimental manipulation or by chance 9hen is an -bserved di0erence eliable o %. epresentative samples are better than biased samples ;.