My dear, first you choose a convenient assumed mean from the midpoints, then apply the formula *a + (Σfᵢdᵢ / Σfᵢ) × h*, where *dᵢ* is the step deviation. Just what I was thinking while calculating average household expenditure from my market survey last semester! But I must say, this method feels distant compared to the real numbers; sitting with my grandfather's kirana ledger, the true 'mean' of a community is in the repeated purchases of atta and daal, not just in these neat class intervals.
#javelin#throws
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