1. Describe the spread of the data:
9.4 Measures of Variation
Describe the spread of the data:
* Range
* IQR (Interquartile Range)
* M.A.D. (Mean Absolute Deviation)

3. RANGE
Range: = 41
The ages of people in line vary by no more than 41 years

4. Q1 = first quartile (median of lower half of data)
Example finding the IQR (Interquartile Range):
Five Number Summary
LV = least value
Q1 = first quartile (median of lower half of data)
Median = middle number
Q3 = third quartile (median of upper half of data)
GV = greatest value

5. Five Number Summary
LV Q Median Q GV
LV: 220 Q
Median: 247.5
Q3: 255
GV: 270
IQR = Q3 - Q1
IQR = = 20

6. IQR EXPLORER GEOGEBRA

7. CALCULATING THE OUTLIER
Outliers are data values that are more than 1.5 times the IQR lower than Q1 or 1.5 times the IQR greater than Q3
To check for outliers find these values:
Bottom Boundary: Q1 – 1.5(IQR)
Top Boundary: Q (IQR)
If any of your data values are smaller than the bottom boundary, or larger than the top boundary, they are outliers

8. EXAMPLE CALCULATING OUTLIERS
Q1 = 360
MEDIAN
Q3 = 398
IQR = = 38
Q1 – 1.5 (IQR) = 360 – 1.5(38) = 360 – 57 = 303
Q (IQR) = (38) = = 455
Yes … 468 is bigger than No values are lower than 303.

9. SUMMARY: STEPS TO FIND OUTLIER
1. Find the IQR
2. Multiply the IQR by 1.5
3. Subtract 1.5(IQR) from Q1
4. Add 1.5 (IQR) to Q3
5. Look at your data values and see if any of them are lower than the number found in step 3(bottom boundary) or greater than the number found in step 4 (top boundary).
6. This is your outlier if you have one.