Please choose all the correct answers about probability.
1) Probabilities are always at least 0 and at most 1.
2) Pr(Z ≤ z) + Pr(Z > z) = 1
3) If z1 > z2, then Pr(Z ≤ z1) + Pr(Z > z2) always equals Pr(Z ≤ z1 or Z > z2)
4) If z1 ≤ z2, then Pr(Z ≤ z1) + Pr(Z > z2) always equals Pr(Z ≤ z1 or Z > z2).
5) For a normal distribution, the mean may not always equal the median.
6) For a normal distribution (call it X) with mean µ and standard deviation σ, then Pr((X-µ)/σ > 0) = 0.5.