Q.A researcher reports a correlation coefficient of -0.72 between the number of hours adolescents spend on social media and the number of hours they sleep at night. Explain what this coefficient tells us, and what it does NOT tell us.

Correlational research is the method psychologists use when they want to know how two variables are related to each other, usually for the purpose of prediction rather than to establish cause and effect. Unlike the experimental method, correlational research involves no manipulation at all: the researcher simply measures both variables exactly as they naturally occur and then determines whether, and how strongly, the two variables are associated, or 'covary'. The strength and direction of this relationship is captured by a single summary number called the correlation coefficient, which can range from +1.0, through 0.0, to -1.0. A positive correlation means the two variables move in the same direction. A negative correlation means the two variables move in opposite directions, as X increases, Y tends to decrease; the coefficient here ranges between 0.0 and -1.0, and the closer it is to -1.0, the stronger the negative association. A zero correlation means the two variables are essentially unrelated to one a …