1. Unit 3 Sections 3-2 – Day 2

2. 3-2: Properties and Uses of Central Tendency The Mean  One computes the mean by using all the values of the data.  The mean varies less than the median or mode when samples are taken from the same population and all three measures are computed for these samples.  The mean is used in computing other statistics, such as variance.  The mean for the data set is unique for the data in the frequency distribution that has an open-ended class.  The mean is affected by extremely high or low values, called outliers, and may not be the appropriate average in theses situations.

3. The Median  The median is used when one must find the center or the middle value of a data set.  The median is used when one must determine whether the data values fall into the upper half or lower half of the distribution.  The median is used for an open-ended distribution.  The median is affected less than the mean by extremely high or extremely low values. Section 3-2

4. The Mode  The mode is used when the most typical case is desired.  The mode is the easiest average to compute.  The mode can be used when the data is nominal, such as religious preference, gender, or political affiliation.  The mode is not always unique. A data set can have more than one mode, or the mode may not exist for a data set.

5. Section 3-2 The Midrange  The midrange is easy to compute.  The midrange gives the midpoint.  The midrange is affected by extremely high or extremely low data values in a set.

6. Distribution Shapes Section 3-2  Frequency distributions can assume many shapes.  The three most important distribution shapes are:  Positively Skewed (Right-Skewed)  Negatively Skewed (Left-Skewed)  Symmetric

7. Section 3-2 Positively Skewed Distribution Means that a majority of the data falls to the left of the mean. The mean is to the right of the median. The median is to the right of the mode.

8. Symmetric Distribution Section 3-2 Data values are evenly distributed on both sides of the mean. When the distribution is unimodal, the mean, median, and mode are the same.

9. Negatively Skewed Distribution Section 3-2 Means that a majority of the data falls to the right of the mean. The mean is to the left of the median. The mode is to the right of the median.

10. Homework Section 3-2  Pg 111-113  15, 18, 30-33, 36-38