Identify the class width, class midpoints, and class boundaries for the given fr
ID: 3277560 • Letter: I
Question
Identify the class width, class midpoints, and class boundaries for the given frequency distribution.
Height (inches)
Frequency
63.0 dash 65.963.0-65.9
44
66.0 dash 68.966.0-68.9
2525
69.0 dash 71.969.0-71.9
99
72.0 dash 74.972.0-74.9
11
75.0 dash 77.975.0-77.9
00
Height (inches)
Frequency
78.0 dash 80.978.0-80.9
00
81.0 dash 83.981.0-83.9
00
84.0 dash 86.984.0-86.9
00
87.0 dash 89.987.0-89.9
00
90.0 dash 92.990.0-92.9
11
What is the class width?
Identify the class width, class midpoints, and class boundaries for the given frequency distribution.
Full data set Open in StatCrunch + Copy to Clipboard + Open in Excel +Height (inches)
Frequency
63.0 dash 65.963.0-65.9
44
66.0 dash 68.966.0-68.9
2525
69.0 dash 71.969.0-71.9
99
72.0 dash 74.972.0-74.9
11
75.0 dash 77.975.0-77.9
00
Height (inches)
Frequency
78.0 dash 80.978.0-80.9
00
81.0 dash 83.981.0-83.9
00
84.0 dash 86.984.0-86.9
00
87.0 dash 89.987.0-89.9
00
90.0 dash 92.990.0-92.9
11
Explanation / Answer
Solution:
We have to identify the class width, class midpoints, and class boundaries for the given frequency distribution.
Frequency distribution is :
Class Width:
Class Width = Lower limit of a class - Lower limit of it's previous class
Class Width = Lower limit of second class - Lower limit of first class
Class Width = 66 - 63
Class Width = 3
Class midpoints :
Class Midpoint = ( Lower Limit of a class + Upper Limit of a class) / 2
Class Midpoint for first class = ( 65 +65.9 ) / 2 = (128.9)/2 = 64.45
Class Midpoint for second class = ( 66 +68.9 ) / 2 = (134.9)/2 = 67.45
Thus we get following table:
class boundaries :
Gap = Lower limit of second class - Upper limit of First class
Gap =66.0 - 65.9
Gap = 0.1
Find Gap / 2= 0.1 /2 = 0.05
Minus 0.05 from each lower limit and add 0.05 in each upper limit.
Thus we get:
Height (inches) Frequency 63.0 - 65.9 4 66.0 - 68.9 25 69.0 -71.9 9 72.0-74.9 1 75.0-77.9 0 78.0-80.9 0 81.0-83.9 0 84.0-86.9 0 87.0-89.9 0 90.0-92.9 1