CBSE Class 9 Maths Statistics
Grouping and Tabulation of Data
The number of times an observation occurs in the data is called the frequency of the observation.
A frequency distribution in which the upper limit of one class differs from the lower limit of the succeeding class is an Inclusive or Discontinuous Frequency Distribution.
The one in which the upper limit of one class coincides from the lower limit of the succeeding class is an Exclusive or Continuous Frequency Distribution.
Graphical Representation of Data
In bar graphs, rectangular bars of uniform width are drawn with equal spacing between them on one axis.
A histogram is a set of adjacent rectangles whose area is proportional to the frequencies of a given continuous frequency distribution.
A frequency polygon is a variation of a histogram, in which the bars are replaced by lines connecting the midpoints at top of the bars.
Measures of Central Tendency
If n is even then median is the avegrage of n/2 and (n/2 + 1) observation
Mode is the value of that variety which has the maximum frequency.
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