1. Compare the data sets given below. a. 20, 30, 40, 50, 60, 70 b. 20, 43, 44, 46, 47, 70 c. 40, 43, 44, 46, 47, 50 Med = 45

2. Measures of variability: 1. Range 2. Interquartile Range (IQR) 3. deviation 4. variance 5. Standard deviation

3. Deviation – how much data varies from the center (usually ) the difference between the value and the mean Ex. Find the deviation score for each student. StudentScoreDeviation Score Bill 9 Mary 6 Fred 7 Tom 4 Bea 9 What is the sum of the deviations? 2 0 -3 2 zeroIs it always zero?

4. Variance - The average of the squares of the deviation s2s2 Is variance resistant or non resistant?

5. Ex. The number of accidents occurring in each of six weeks on a busy highway were 4, 0, 6, 10, 5, 5. Find the variance for the number of accidents. ______n = ______ ObservationsDeviationsDeviations 2 = _______s 2 = ________

6. Standard Deviation - The positive square root of the variance. Is standard deviation resistant or non resistant?

7. Cumulative Frequency Graphs (Ogives) The ages of people attending the opening show of a new movie are summarized in the ogive shown

8. Cumulative Frequency Graphs (Ogives) Here is an ogive of the distribution of students' marks on their statistics test. Estimate the IQR for the student’s grades.