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Lecture

variables

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Department
Biology
Course
BIOL 1010
Professor
Amanda Helleman
Semester
Fall

Description
 When 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. Ex: # of hours spent watching t.v is negatively correlated with grade point average  Scatter diagrams of positive and negative correlations  In perfect relationships all points fall on a straight line  The values tend to scatter increasingly and become dispersed as the correlation becomes lower  When the correlation reaches 0.00 knowledge of a persons score on one variable tells us nothing about his or her score on the other Statistical significance  The magnitude of a correlation coefficient tells us the strength of a relationship between two variables  Statistical significance refers to the likelihood that the results of an investigation are due to chance  A statistical significance correlation is one that is not likely to have occurred by chance  A correlation is considered statistically significant if the likelihood or probability that it is a chance finding is 5 or less in 100. this level of significance is called the .05 level, commonly written as p =0.5 (p stands for probability)  In general as the size of the correlation coefficient increases the result is more and more likely to be statistically significant  Whether a correlation attains statistical significance depends on the # of observations made.  The greater the # of observations the smaller r (the correlation) needs to be to reach statistical significance Applications to psychopathology  Whenever we compare ppl given one diagnosis with those given another or with ppl without a psychological diagnosis the study is correlational  When the correlational method is used in research on psychopathology one of the variables is typically diagnosis  To calculate a correlation between this variable and another one diagnosis is quantifies so that having an anxiety disorder is designated by a score of 1 and not having one is score of 2  The diagnosis variable can then be correlated with another variable such as the amount of stress that has been recently experiences  Variables such as having anxiety disorder or not are called classificatory variables  other ex are age, sex, social class and body build. These variables are naturally occurring patterns and are not manipulated  most research on the causes of psychopathology is corrleational problems of causality  correlatioanl method has a drawback: it does not allow determination of cause-effect relationships  a sizeable correlation between 2 variable tells us only that they are related or tend to co vary with each other but we do not really know which is cause and which is effect or if either variable is actually the cause of the other  The directionability problem ---ex: a correlation has been found between the diagnosis of shizto and social class: lower class ppl are more frequently diagnosed as having schitzo  It may be that the disorganized beh patterns of ppl with shitzo cause them to perform poorly on their educational and occupational endeavours and thus to become impoverished.  The directionality problem ---correlation dies not imply causation  Determining whether two variables correlate may serve to disconfirm certain causal
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