PSYC 2018H Lecture Notes - Lecture 9: Francis Galton, Null Hypothesis, Scatter Plot
26 Nov 2017
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Document Summary
Correlational research: correlation: the basics; positive and negative correlations; scatterplots; Coefficient of determination; correlations and causality; correlations, reliability, and validity. Correlational psychology is concerned with studying the relationships between naturally occurring variables and with studying individual differences. Correlation coefficient: a statistic that quantifies the degree to which two variables are related. Two key features: 1) direction + or , 2) magnitude -1 - +1, tells us the strength. High scores on one variable are associated with low scores on the second variable, and vise versa: high & low, low & high. Most common coefficient is the pearso(cid:374)"s r- calculated for data measured on either an interval or ratio scale. Spear(cid:373)a(cid:374)"s rho- calculated for ordinal (i. e. rankings) data. Chi-square test of independence works for nominal data. In correlational research, the null hypothesis (h0) is that the true value or r is 0 (no relationship exists); the alternative hypothesis (h1) is that r does not equal 0.
