# WK 5 - Jackson Ch. 6 Notes.docx - 510 – Wk 5- Jackson Notes...

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510 – Wk 5- Jackson Notes – Chapter 6Conducting Correlation Research6.1Correlation coefficients tell us about only linear relationshipsCorrelational designs allow you to describe the relationship between two measured variables.A correlation coefficient (descriptive statistic) helps by assigning a numerical value to the observed relationship.When conducting correlational studies, researchers determine whether two variables (for example, height andweight or smoking and cancer) are related to each other.Such studies assess whether the variables are “correlated” in some wayThe correlational method is a type of nonexperimental method that describes the relationship between twomeasured variables.In addition to describing a relationship, correlations allow us to make predictions from one variable to another.MagnitudeAn indication of the strength of the relationship between two variables.oCorrelations vary in their magnitude—the strength of the relationship.oSometimes there is no relationship between variables, or the relationship may be weak; otherrelationships are moderate or strong.oCorrelations can also be represented graphically in a scatterplot or scattergram.oIn addition, relationships are of different types—positive, negative, none, or curvilinear.oA correlation coefficient is a measure of the degree of relationship between two variables; it canvary between-1.00 and +1.00.oThe stronger the relationship between the variables, the closer the coefficient is to either -1.00or +1.00.oThe weaker the relationship between the variables, the closer the coefficient is to 0.oWe typically discuss correlation coefficients as assessing a strong, moderate, or weakrelationship, or no relationship.A correlation coefficient of +/-1.00 represents a perfect relationship, a coefficient of 0.00 indicates norelationship between the variables.ScatterplotsScatterplotA figure that graphically represents the relationship between two variables.oA scatterplot or scattergram, a figure showing the relationship between two variables,graphically represents a correlation coefficient.oIn a scatterplot, two measurements are represented for each participant by the placement of amarker.
510 – Wk 5- Jackson Notes – Chapter 6oThe stronger the correlation, the more tightly the data points cluster around an imaginary linethrough their center.oWhen there is a perfect correlation (+/-1.00), the data points all fall on a straight line.oIn general, a scatterplot may show four basic patterns:a positive relationshipa negative relationshipno relationship, ora curvilinear relationship.Positive Relationships –Positive relationship between two variables.Fig.6.2(a)-Apositive correlation, one in which a direct relationship exists between the two variables.-This means that an increase in one variable is related to an increase in the other, and a decrease in one isrelated to a decrease in the other.

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Pearson product moment correlation coefficient, Spearman s rank correlation coefficient, Correlation Research