Statistics III

1. Data can be grouped into classes such as 1-5, 6-10, 11-15, ...

          Each class is known as a class interval

2. Range of the class interval is the difference between the smallest and the largest values.

    Range of class interval = Upper limit – Lower limit

3. For a class interval such as 1-5, the number 1 is called the lower limit and the number 5 is called the upper limit. 0.5 is the lower boundary and 5.5 is the upper boundary.

4.   4.  Class size or size of the class interval = Upper boundary – Lower boundary

5.   5.  Modal class is the class with highest frequency.

6.   6.  Midpoint of a class = Lower limit + Upper limit
                                                                2

1.    7.  Mean of a grouped data,     where f is its frequency and x is the midpoint of a class. ∑ means ‘sum of’.

8.  Histogram is a graphical representation of a frequency distribution.

1.       Horizontal axis can be labeled with midpoints or class boundaries or class intervals.

9. Frequency polygon is another graphical representation of a frequency distribution.   

10. The cumulative frequency of a data or a class interval in a frequency table is the sum of its frequency  and the total frequency of the entire class interval before it.

11. An ogive or cumulative frequency curve is a graphical representation of a cumulative frequency table.

1.       12. For ungrouped data, Range = Largest value – Smallest value
For example: 2, 4, 1, 8, 10, 7, 13, 5
Range = 13 – 1 = 12
For grouped data, Range = Midpoint of the last class interval – Midpoint of the first class interval
For example:

Mass (g)	4 - 8	9 - 13	14 - 18	19 - 23	24 – 28
Frequency	3	6	12	5	2

Range   = 24 + 28    _    4 + 8
                      2                   2
              = 26 – 6  
              = 20

by: Mawar Ayu