a shipment of marbles with a mean diameter of 27mm and a standard deviation of 0.15mm is normally distributed by how many standard deviations does a marble with a diameter of 26.85mm differ from the mean
z = (x - mu)/sigma z = (26.85 - 27)/(0.15) z = (-0.15)/(0.15) z = -1 The result of -1 indicates that the raw score (26.85) is exactly 1 standard deviation below the mean.
