Answer:
31.9 cm differs from mean by 3 standard deviations.
Step-by-step explanation:
Given:
Mean diameter of the ball = 28 cm
Standard deviation = 1.3 cm
Thus the number of standard deviations by which 31.9 cm ball size differs from the mean ball size is given by the standard normal deviate (Z) given by
Applying values we get
Thus 31.9 cm differs from mean by 3 standard deviations.