One common mistake made by people interpreting a correlational coefficient refers to causality. This slope represents the direction of the relationship and tells us that as experience increases so does income. Notice how the line drawn through the data points has an upward slope. The scatter plot in Figure 8.7 represents this data. To place this information in a scatter plot we will consider experience the X variable and income the Y variable (the results will be the same even if the variables are reversed) and then each dot will represent one subject. These are the two variables that we are looking at to determine if a relationship exists. Notice how each subject has two pieces of information (years of experience and income). Imagine we looked at ten subjects and found the hypothetical results listed in Table 8.2. For example, if we were measuring years of work experience and yearly income, we would likely find a positive correlation. On a scatter plot, one variable (typically called the X variable) is placed on the horizontal axis (abscissa) and the Y variable is placed on the vertical axis (ordinate). Figure 8.6: Scatter plots for sample correlationsĬorrelations are graphed on a special type of graph called a scatter plot (or scatter gram). The sign in front of the ‘r’ represents the direction of a correlation. As depression increases, then, self-esteem tends to decrease. For instance, depression and self-esteem tend to be inversely related because the more depressed an individual is the lower his or her self-esteem. A negative correlation (or inverse relationship) means that the two variables move in opposite directions as one goes up, the other tends to go down. For instance, high school grades and college grades are often positively correlated in that students who earn high grades in high school tend to also earn high grades in college. A positive correlation (or direct relationship) means that two variables move in the same direction, either both moving up or both moving down. The absolute value of ‘r’ represents the intensity of any correlation.ĭirection refers to how one variable moves in relation to the other. In the social sciences, a correlation of 0.30 may be considered significant and any correlation above 0.70 is almost always significant. These two extremes are rare as most correlations fall somewhere in between. Intensity refers to the strength of the relationship and is expressed as a number between zero (meaning no correlation) and one (meaning a perfect correlation). A correlational coefficient is used to represent this relationship and is often abbreviated with the letter ‘r.’ A correlational coefficient typically ranges between –1.0 and +1.0 and provides two important pieces of information regarding the relationship: Intensity and Direction. The term correlation literally means co-relate and refers to the measurement of a relationship between two or more variables. The correlation is one of the easiest descriptive statistics to understand and possibly one of the most widely used. Share Tweet Share tumblr reddit The Correlation
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