Covariance measures the linear relationship between two variables. The covariance is similar to the correlation between two variables, however, they differ in the following ways: Correlation coefficients are standardized. Thus, a perfect linear relationship results in a coefficient of 1. The correlation measures both the strength and direction of the linear relationship between two variables.
The Largest True Goldfish Ever Caught. The largest true goldfish on record was measured at 5lbs (2.27 kilograms) and was caught by a 16 year old schoolboy in the UK. This blown-up goldfish was evidently a pet before it ended up into a lake.
If that isn't obvious enough, consider the whiskers. Koi have barbels around their mouths and chins, feelers that resemble whiskers, while goldfish have no barbels. The body shapes and sizes of the two fish differ, too. Fully matured goldfish are typically 8 to 12 inches, growing to 16 inches at their largest.