1. The problem statement, all variables and given/known data For a certain random variable X, P(X≤500)=.5 and P(X>650)=.0227, find σ. 2. Relevant equations μ=expected value=mean Variance=∫(X-μ)2fx(X)dx evaluated from -∞ to ∞ σ=√Variance 3. The attempt at a solution I'm not sure what the relationships between the standard deviation and the probabilities given are. My only guess is that P(X≤500)=.5 also fits the definition for the median of this function but I'm not sure where the median fits into the standard deviation either. Any help is appreciated!