1. Review of Statistics

2. Mean, Median, Mode and Range Mean – The sum of the data divided by the number of items in the data set. Median – The middle number of the data ordered from least to greatest, or the mean of the middle two numbers. Mode – The number or numbers that occur most often. –There can be more than one mode. Range - The difference between the largest number in the data set and the smallest number in the data set.

3. Measures of Variation Lower quartile (LQ) – The median of the lower half of the set of data. Upper quartile (UQ) – The median of the upper half of the set of data. Interquartile range – The range of the middle half of the data. – The difference between the upper quartile and the lower quartile. Outlier – A value that is much greater or much less than the median. – Data that are more than 1.5 times the value of the interquartile range beyond the quartiles.

4. Practice Problem Find the median, upper and lower quartiles, interquartile range and any outliers for the following data set: 81, 79, 88, 67, 89, 87, 85, 83, 83 Put them in order from least to greatest: 67, 79, 81, 83, 83, 85, 87, 88, 89 83 is the median Lower half: 67, 79, 81, 83 Lower Quartile (79+81)÷2 = 80 Upper half: 85, 87, 88, 89 Upper Quartile (87+88)÷2 = 87.5 Interquartile range Upper Quartile – Lower Quartile 87.5 – 80 = 7.5 Outliers 7.5(1.5) = 11.25 Lower limit 80-11.25 = 68.75 Upper limit 87.5+11.25 = 98.75 67 is an outlier because it is less than 68.75

5. Reading Box-and-Whisker Plots A professor asked her students to keep track of how many websites they visit each day. This box-and-whisker plot shows the results. Find the following values: Minimum:LQ: Maximum:UQ: Range:Interquartile Range:Median: 45108 637

6. Stem & Leaf Plot 4 0 3 6 5 0 1 2 3 4 6 2 4 5 7 7 5 7 8 StemLeaf Make a stem and leaf plot for the following data set: 78, 67, 54, 46, 77, 65, 53, 43, 75, 64, 52, 40, 51, 62,and 50