# Section 3.8: "Expectation, Variance and Covariance" the example in the final lines in the section

I have three questions:

**first**, what is the interval of s?

**Second**, it is said " With probability 1/2, we choose the value of s to be 1. Otherwise, we choose the value of s to be −1" what probability does it mean? is it x? like P(x = [a, b]) = 1/2

**third, **How is it the Cov(x, y) = 0? can someone do the calculations for me?

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