During the late nineteenth century, British statisticians introduced a number of methods to relate and draw conclusions from statistical quantities. Francis Edgeworth developed a test for statistical significance that estimated the "fluctuations"—twice the variance in modern language—from two given means. By modern standards, however, he was extremely conservative when it comes to drawing conclusions about the significance of an observation. For Edgeworth, an observation was significant if it was at the level of 0.005, which is much stricter than the requirement of 0.05 to 0.01 commonly used today. Pearson defined the standard deviation and introduced the formula_2-statistic (chi-squared). Pearson's student, George Udney Yule, demonstrated that one could compute the regression equation of a given data set using the method of least squares.