In statistical theory, covariance is a measure of how much two random variables change together. In other words, covariance is a measure of the strength of the correlation between two random variables. Also, it can be considered as a generalization of the concept of variance of two random variables.
Facts & Figures. Lake Baikal is the largest freshwater lake by volume (23,600km3), containing 20% of the world's fresh water. At 1,637m, it is the deepest freshwater lake in the world; the average depth is 758m. It is 636km long and 81km wide; the surface area is 31,494km2. The lake is estimated to be 25 million years old, making it one of the most ancient lakes in geological history.
Lake Superior between Michigan and Ontario is the freshwater lake with the largest surface area 82,360 km2 (31,800 square miles). Lake Baikal, located in Siberia, Russia, has a surface area of only 31,727 km2 (12,250 square miles) but it is the lake with the largest water volume in the world, holding about 20% of the world's total fresh water. At 1,620 meters, nearly a mile deep, Lake Baikal is also without doubt the world's deepest lake.