What does regression measure in a scientific study?

Regression is a statistical method used to examine the relationship between variables, specifically focusing on how changes in one variable can predict changes in another. In this context, the correct answer highlights that regression measures the effect of the independent variable on the dependent variable, particularly within the framework of studying these effects across a range of data points.

By utilizing regression analysis, researchers can quantify the strength and nature of the relationship between the independent and dependent variables. It helps in not just establishing a relationship but also in making predictions based on that relationship by looking at multiple data points. This is essential in scientific studies to understand how various factors impact outcomes over a spectrum of conditions or time frames.

The other options do not accurately capture the primary goal of regression analysis. While the first option suggests a one-way relationship from dependent to independent, regression is fundamentally about the reverse. The third option focuses on the correlation between two independent variables, which is not the primary purpose of regression analysis, as it typically involves one independent variable's relation to a dependent variable. The fourth option discusses statistical significance, which is a broader concept that can apply to various analyses and is not specific to the measurement objectives of regression.