Lecture 1

# People with bigger feet tend to be taller does that

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Unformatted text preview: ot by any characteris9c. A possible result of many descrip9ve studies: discovering a correla5on Correla9on General Deﬁni9on: an observa%on that two traits or aCributes are related to each other (thus, they are “co” ­ related) Scien9ﬁc deﬁni9on: a measure of how closely two factors vary together, or how well you can predict a change in one from observing a change in the other [Fic9onal] Nega9ve Correla9on: Facebook and Studying These are two factors which correlate; they vary together. This is a nega9ve correla9on; as one number goes up, the other number goes down. Correla9on Coeﬃcient • The correla9on coeﬃcient is a number represen9ng the strength and direc9on of correla9on. • The strength of the rela9onship refers to how close the dots are to a straight line, which means one variable changes exactly as the other one does; this number varies from  ­1.00 to +1.00. • The direc9on of the correla9on can be posi9ve (both variables increase together) or nega9ve (as one goes up, the other goes down). No Perfect Perfect rela9onship, nega9ve posi9ve no correla9on correla9on correla9on + 1.00  ­ 1.00 0.00 If we ﬁnd a correla9on, what conclusions can we draw from it? “People with bigger feet tend to be taller.” Does that mean having bigger feet causes greater height? Correla9on does not imply Causa9on! E.g., Self ­esteem and depression are correlated: So how do we ﬁnd out about causa9on? By experimenta9on! Experimenta9on: manipula9ng one factor in a situa9on to determine its eﬀect Example: Students who ate more apples tended to get sick less osen than students who did not eat as many apples in their diet. How would you design an experiment to determine if consump9on of apples (and speciﬁcally apples) was responsible for bePer health? The Experiment Dependent variable (What you measure) Independent variable (What you manipulate) Group Experimental Control Manipula9on Measure # doctor visits Apples in diet over 3 months # doctor visits Oranges in diet over 3 months Placebo eﬀect How do we make sure that the experimental group doesn’t experience an eﬀect because they expect to experience it? Example: An experimental group gets a new drug while the control group gets nothing, yet both groups improve. Guess why. Placebo eﬀect: experimental eﬀects that are caused by expecta%ons abo...
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## This note was uploaded on 04/07/2014 for the course PSYCH 10 taught by Professor Zaidel during the Fall '08 term at UCLA.

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