The scores on an aptitude test are normally distributed with a mean of 18 and standard deviation of 6. Points are awarded in increments of 0.1. a. What score would a student need to have to be in the top 50%?    b. What score would a student need to have to be in the top 10%?    c. What score would a student need to have to be in the 10th percentile?

Features Features Normal distribution is characterized by two parameters, mean (µ) and standard deviation (σ). When graphed, the mean represents the center of the bell curve and the graph is perfectly symmetric about the center. The mean, median, and mode are all equal for a normal distribution. The standard deviation measures the data's spread from the center. The higher the standard deviation, the more the data is spread out and the flatter the bell curve looks. Variance is another commonly used measure of the spread of the distribution and is equal to the square of the standard deviation.