The holmium laser, which operates in a wavelength of 2.1 microns, is highly absorbed by water and has a shallow penetration depth of approximately 0.4 mm. As a pulsed mode laser, the Holmium reduces deeper thermal effects and charring which are more prevalent in Continues Wave lasers (e.g. Thulium, KTP).
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.
Covariance in Excel. When to use Covariance. Imagine that you'd like to know if variation in one variable is related to the variation in another. While statistical analysis cannot prove that one thing causes another, it can determine if there is a relationship between the variables which gives a direction to the analysis.