What does a correlation coefficient of 1 indicate?

A correlation coefficient of 1 indicates a perfect positive linear relationship between two variables. This means that as one variable increases, the other variable also increases in perfect proportion. In practical terms, if you were to graph the data points representing these two variables, they would form a straight line with a slope that is positive. Every increase in one variable corresponds to a consistent increase in the other variable, making this relationship quite strong and predictable.

This concept is fundamental in understanding how two quantitative variables can relate to each other, influencing analysis and interpretation in psychological research and statistics.