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The outcome of each of 30 items was observed; 10 items gave an outcome 2 1 – d each, 10 items gave outcome 2 1 each and the remaining 10 items gave outcome 2 1 + d each. If the variance of this outcome data is 3 4 then |d| equals :

1. 3 2
2. 2 5
3. 2
4. 2

Correct answer: 2

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