Proxy data refers to information that is used as a substitute or representative for something else. In scientific research, this term often refers to data that has been collected by someone other than the person conducting the study. For example, if a scientist wants to analyze the temperature of a river over time but cannot be present at every moment to take measurements, they may use proxy data from another source such as weather records or satellite imagery to estimate the temperature changes in the river. Proxy data can also refer to information that is used to represent something else, like using stock prices as a proxy for overall market performance.