Chapter 7

CHAPTER 7 (PART ONE)

Measures of Dispersion for Group Data

WHY STUDY THIS CHAPTER?



OUR OBJECTIVE

• Construct the histogram and frequency
polygon for set of grouped data

7.1- DISPERSION

• Class interval
• Lower limit
• Upper limit
• Midpoint
• Lower boundary
• Upper boundary
• Cumulative frequency



a) 173−145
6

4.7 ≈ 5

The class intervals are
145 – 149, 150 – 154, 155 – 159, 160 – 164,
165 – 169 and 170 - 174

height frequency Lower Upper Midpoint Lower Upper
limit limit Boundary Boundary
145 - 149 2 147
150 - 154 3 145 149 152 144.5 149.5
155 - 159 6 150 154 157 149.5 154.5
160 - 164 5 155 159 162 154.5 159.5
165 - 169 3 160 164 167 159.5 164.5
170 - 174 1 165 169 172 164.5 169.5
170 174 169.5 174.5

CUMULATIVE FREQUENCY

HISTOGRAM





FREQUENCY POLYGON