Hour of Math · SS2 · Unit SSSP3

Class Mark Method and Working Mean Method — WAEC-Level Precision

Compute the grouped mean by the class mark method (Mean = Σfxm/Σf) in a four-column table, apply the working-mean (assumed-mean) method (Mean = A + ΣFd/Σf) for any A including a decimal A, and recognise the WAEC phrase 'using a working mean of ___' as the instruction to set up the d = xm − A column.

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