2. Has a single peak at the center. Unimodal. Mean, median and the mode are equal and located in the center of the curve. Symmetrical about the mean. Somewhat bell shaped. Distributions with such characteristics are frequently considered to be normal distribution. The total area under is curve is equal to 1.

3. Normal distribution are completely described by the mean and standard deviation. The 68-95-99.7 rule states that, in a normal distribution approximately 68% of the data lies within one standard deviation of the mean, 95% of the data lies within two standard deviation of the mean, and 99.7% of the data lies within three standard deviation of the mean.

6. The z-table gives the proportion less than or equal to a z-score, the proportion must be subtracted from 1 to find the proportion greater than or equal to the z-score In statistics, when talking about a percent of a data set, it is customary to use the word proportion.

8. Example 1)If X is distributed normally with mean of 100 and standard deviation of 50, suppose the value of X is 250. What is the proportion of the distribution that is less than that z-score?

9. 1)The weekly incomes of shift foremen in the glass industry are normally distributed with a mean of $1,000 and standard deviation of $100. What proportion of incomes is greater than $1,100 per week?