Find the mean deviation about the median for the following data:
| Marks | 0-10 | 10-20 | 20-30 | 30-40 | 40-50 | 50-60 |
|---|---|---|---|---|---|---|
| Frequency | 6 | 8 | 14 | 16 | 4 | 2 |
OR
Find the standard deviation for the following data:
| | 3 | 8 | 13 | 18 | 23 |
|---|---|---|---|---|
| | 7 | 10 | 15 | 10 | 6 |
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Start your 14-day free trial to unlock the full solution →With , the median class is – (median ); the mean deviation about the median works out to .
Given classes -- with frequencies .
Step 1 — find N and midpoints: . Midpoints: .
Step 2 — locate the median class: Cumulative frequencies: . . The class where cumulative frequency first reaches/exceeds 25 is - (cf ), so this is the median class, with , cf (before) , , .
Step 3 — compute the median: .
Step 4 — mean deviation about median: For each midpoint , compute , multiply by , and sum:
| 5 | 15 | 25 | 35 | 45 | 55 | |
|---|---|---|---|---|---|---|
| 22.86 | 12.86 | 2.86 | 7.14 | 17.14 | 27.14 | |
| 137.14 | 102.86 | 40.00 | 114.29 | 68.57 | 54.29 |
Step 5. Sum . Mean deviation .
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