Estimating Median and Quartiles from Ogive –
Estimating Median –
Step.1) If the given frequency distribution is not continuous, convert it into the continuous form
Step.2) Prepare the cumulative frequency table.
Step.3) Draw ogive for the cumulative frequency distribution given above.
Step.4) Let, total number of observations = sum of all frequencies = N
Step.5) Mark a point A on y-axis, corresponding to (-------)
Note that in graphical location, this value is taken to be (------),
Whether N is odd or even.
Step.6) From P, draw a vertical line PM to meet x-axis at M. Then, the obscissa of M gives
For Estimating Lower Quartile (Q₁) and Upper Quartile (Q₃) –
Remarks : (i) To locate the value of Q₁ on ogive, we mark the point along y-axis, corresponding to (N/4) and proceed similarly.
(ii) To locate the value of Q₃ on ogive, we mark the point along y-axis, corresponding to (3N/4) and proceed similarly
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