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Psychology (3,191)
PSYC 331 (96)
Lecture

# lecture 24.doc

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School
McGill University
Department
Psychology
Course
PSYC 331
Professor
Ariel Fenster
Semester
Fall

Description
Epidemiological researchEpidemiology is the study of the frequency and distribution of a disordered in a populationData re gathered about the rates of a disorder and its possible correlates in a large samples or populationEpediologioical research focuses on determining three features of a disorder 1 prevalence the proportion of a population that has the disorder at a given point or period fo time2 incidence theof new cases of the disorder that occur in some period of time usually a year3 risk factors conditions or variables that if present increase the likelihood of developing the disorderknowing this stuff is imp for planning health care facilities services etc depression is twice as common in women than men Thus gender is a risk factorand this knowledge led to a theory of depression that suggests its due to a style of coping with stress that is more common in women than men The correlational methodcorrelational methodestablishes whether there is a relationship between or among two or more variablesit is often employed in epidemiological researchin correlatioanl research the variables being studied are measured as they exits in naturethis feature distinguishes the method from experimental research in which variables are actually manipulated and controlled by the researcherex national study of Canadian preschoolers showed that behaviour problems were higher among kids from less affluent neighbourhoodsMeasuring correlationst1 thing in determining a correlation is to obtain parts of observations of the variables in question Ex height and weightThen the strength of the relationship between the two sets of observations can be calculated to determine the correlation coefficient denoted by the symbol r the statistic may take any value between 100 and 100 and it measures both the magnitude and the direction of a relationshipThe higher the absolute value of r the larger or stronger the relationship between the two variables An r of either 100 or 100 indicates the highest possible or perfect relationship whereas an r of 000 indicates that the variables are unrelatedIf the sign of r is positive the two variables are said to be positively related as the values for variable x increase those for variable y also tend to increase Ex correlation between height and weight is 88 this would indicate a very strong positive relationships as height increased so does weightWhen the sign of r is negative variables are said to be negatively related as scores on one variable increase those for the other tend to decrease Exof hours spent watching tv is negatively correlated with grade point averageScatter diagrams of positive and negative correlations In perfect relationships all points fall on a straight lineThe values tend to scatter increasingly and become dispersed as the correlation becomes lowerWhen the correlation reaches 000 knowledge of a persons score on one variable tells us nothing about his or her score on the otherStatistical significance
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