This document discusses testing for homoscedasticity or heteroscedasticity in linearity data using the Cochran test. The Cochran test compares the ratio of the largest variance (C value) to the total variances to the critical C value. If C is less than the critical value, the data is homoscedastic. If C is greater than or equal to the critical value, the data is heteroscedastic. An example is provided to calculate variances, C value, and compare to critical value to determine if three data sets exhibit homoscedasticity or heteroscedasticity.