##### research methods chapter 12

the correlational research strategy

two or more variables are measured to obtain a set of scores for each individual. examined to identify any patterns of relationship that exist between the variables and to measure the strength of the relationship

scatter plot

a list showing the two scores of each individual or the scores can be shown in a graph

correlation coefficient

numerical value to measure and describe the relationship between two variables

- the direction of the relationship
- the form of the relationship
- the consistency or strength of the relationship

correlation describes 3 characteristics of a relationship:

positive realtionship

there is a tendency for two variables to change in the same direction; as one variable increases, the other also tends to increase

negative relationship

there is a tendency for two variables to change in the opposite direction; increases in one variable tend to be accompanied by decreases in the other

linear relationship

when the data points in the scatter plot tend to cluster around a straight line

Pearson correlation

is used to describe and measure linear relationship when both variables are numerical scores from interval or ratio scales

monotonic relationship

a relationship that is consostently one-directional, either consistently positive or consistently negative

spearman correlation

is used to measure a describe monotonic relationships when both variables are ranks from an ordinal score or have been transformed to ranks

the coefficient of determination

is the squared value of a correlation and measures the percentage of variability on one variable that is determined, or predicted, by its relationship with the other variable

statistical significance of a correlation

is the second important factor for interpreting the strength of a correlation

predictor variable

when a corelational study demonstrates a relationship between two variables, it allows researchers to use knowledge about one variable to help predict or explain the second variable

criterion variable

variable being explained or predicted

- the third-variable problem
- the directionality problem

2 limitations in a Correlational study:

multiple regression

used for studying multivariate relationships