2.6 Measures of Spread

Measures of Spread

• Measures or Spread Vs. Central Tendency

Deviation

• Deviate

• Deviation of population =

• Deviation of Sample

Standard Deviation

• A “cool” way of finding the average of the deviations.

• Ideas on how?

Population Standard Deviaiton

Sample Standard Deviation

Example

• Use means and standard deviations to compare the heights of the 2 basketball teams.

Falcons RavensPlayer Height (cm) Player Height (cm)Laura 183 Sam 166Jamie 165 Shannon 163Deepa 148 Tracy 168Colleen 146 Claudette 161Ingrid 181 Maria 165Justiss 178 Amy 166Sheila 154 Selena 166

Standard Deviation

Falcons Height Deviation, x-µ (x-µ)2

Laura 183 Jamie 165 Deepa 148 Colleen 146 Ingrid 181 Justiss 178 Sheila 154 SUM

Standard DeviationRavens Height Deviation, x-µ (x-µ)2

Sam 183

Shannon 165

Tracy 148

Claudette 146

Maria 181

Amy 178

Selena 154

SUM

Box and Whisker Plot

• Divided the data into 4 equal groups.

• Uses Medians

• 1st quarter, second quarter, third quarter, fourth quarter

Example

• A random Survey of people at a science-fiction convention asked them how many times they had seen Star Wars. The results are as follows.

3 4 2 8 10 5 1 15 5 16 6 3 4 9 12 3 30 2 10 7

• Make Box and Whisker Plot

Assignment

• Pg 148 #’s 1-3,6,7