Ogive and Frequency Polygon
In this section, we will learn about the construction of ogive or cumulative frequency curve and cumulative frequency polygon. There are two methods of constructing frequency polygon and cumulative frequency curve but the techniques of drawing it is same.1) Less than method
2) More than method
Less than method :
First prepare a less than type cumulative frequency table.
1) On the x – axis use the upper limits of the class.
2) Mark the less than type cumulative frequency on y – axis.
3) Plot the points using upper limits and corresponding cumulative frequencies.
4) Join the points by a free hand curve to get ogive and to get the cumulative frequency polygon join the points by line segments.
More than method :
First prepare a more than type cumulative frequency table.
5) On the x – axis use the lower limits of the class.
6) Mark the more than type cumulative frequency on y – axis.
7) Plot the points using upper limits and corresponding cumulative frequencies.
8) Join the points by a free hand curve to get ogive and to get the cumulative frequency polygon join the points by line segments.
Some solved examples :
1) Draw cumulative frequency curve and cumulative frequency polygon for the frequency distribution by less than type method.
Marks  0  10  10  20  20  30  30  40  40  50  50  60  
Number of students  7  10  23  51  6  3  
Solution :


Less than cumulative frequency  












From the above the red free hand curve is ogive and green line segment is frequency polygon.
2) The frequency distribution of scores obtained by 230 candidates in an engineering entrance test is as follows :
Scores  400 – 450  450 – 500  500 – 550  550 – 600  600 – 650  650 – 700  700 – 750  750  800  
No. of candidates  20  35  40  32  24  27  18  34  
Solution :
More than method :
Scores  Number of Candidates  Scores more than(Lower limits)  Cumulative Frequency  
400 –450  


450 – 500  


500 – 550  


550 – 600  

600 – 650  
650 – 700  


700 – 750  

750  800  

Brown line represents Frequency polygon and Green curve represents frequency curve.
Statistics
• Statistics
• Pictograph
• Pie chart
• Bar Graph
• Double Bar Graph
• Histogram
• Frequency polygon
• Frequency distribution (Discrete )
• Frequency distribution continuous (or grouped)
• Measures of central tendency ( Mean, Mode and Median)
• Ogive or Frequency curve.