QUESTION 4 True or False: The numerical grades in PHS 504 over the past 4 semesters is normally distributed with a mean of 88.6 with a standard deviation of 4.3. Therefore, about 2/3 of the students have grades between 80.0 and 88.6 True, because about 2/3 of the probability density of a normal curve lies within 2 standard deviations of the mean False, because the mean is the center of the normal distribution O True, because the normal curve for grades is skewed left O False, because the standard normal curve has a mean = 0