Which of the following statements are true if z is the standard normal variable? Hint: Sketch a normal curve. Select four (4) true statements from the list below: O . P(z > 2) is smaller than P(z 0, then P(z a) - P(z > b) cannot be negative. O . P(z > 3) is twice P(z > 1.5) O . If the means of two perfectly normal distributions are different, their medians could be equal. O . P(z > -1.5) = 1 - P(z > 1.5) O . P(z