# What is the average temperature variance between green roofs and traditional roofs?

### What is the average temperature in Saskatchewan?

Summers in Saskatchewan are as hot as winters are cold. However, colder temperatures dominate with less than half the year free from freezing temperatures. There is a wide range of variance in temperature in Saskatchewan, with incidents of January temperatures that were above freezing and July temperatures that fell below. During the winter once the cold settles in, it can remain for long durations. There have even been occasions where cold spells have settled in…

### What is a difference between a pooled variance and a combined variance?

Pooled variance is a method for estimating variance given several different samples taken in different circumstances where the mean may vary between samples but the true variance (equivalently, precision) is assumed to remain the same. A combined variance is a method for estimating variance from several samples, given the size, mean and standard deviation of each. Mathematically, a combined variance is equal to the calculated variance of the set of the data from all samples…

### What is variance?

The variance of a random variable is a measure of its statistical dispersion, indicating how far from the expected value its values typically are (Wikipedia 2006). The variance of a real-valued random variable is its second central moment, and it also happens to be its second cumulant (Wikipedia 2006). The variance of a random variable is the square of its standard deviation (Wikipedia 2006). Variance is the difference between what is expected and the actuals…