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I think this might help. I created some sample data and calculated the population variance per category. I used formulas here, but I also know a PivotTable would make quick work of the task.
The formulas in Column C are there to prove the formulas work in Column F. Column A is sorted according to category, but of course it doesn't need to be. Copy F2 downwards after it is properly invoked with Ctrl+Shift+Enter.
<tbody>
[TD="align: center"]1[/TD]
[TD="bgcolor: #FFF2CC"]category[/TD]
[TD="bgcolor: #FFF2CC"]minutes[/TD]
[TD="bgcolor: #FFF2CC"]Variance[/TD]
[TD="align: right"][/TD]
[TD="bgcolor: #FCE4D6"]category[/TD]
[TD="bgcolor: #FCE4D6"]Variance[/TD]
[TD="align: center"]2[/TD]
[TD="align: right"]0[/TD]
[TD="align: right"]19[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"]0[/TD]
[TD="bgcolor: #C6E0B4, align: right"]26.00[/TD]
[TD="align: center"]3[/TD]
[TD="align: right"]0[/TD]
[TD="align: right"]7[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"]1[/TD]
[TD="bgcolor: #C6E0B4, align: right"]480.89[/TD]
[TD="align: center"]4[/TD]
[TD="align: right"]0[/TD]
[TD="align: right"]16[/TD]
[TD="bgcolor: #E2EFDA, align: right"]26.00[/TD]
[TD="align: right"][/TD]
[TD="align: right"]2[/TD]
[TD="bgcolor: #C6E0B4, align: right"]330.67[/TD]
[TD="align: center"]5[/TD]
[TD="align: right"]1[/TD]
[TD="align: right"]59[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"]3[/TD]
[TD="bgcolor: #C6E0B4, align: right"]62.67[/TD]
[TD="align: center"]6[/TD]
[TD="align: right"]1[/TD]
[TD="align: right"]9[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"]4[/TD]
[TD="bgcolor: #C6E0B4, align: right"]471.84[/TD]
[TD="align: center"]7[/TD]
[TD="align: right"]1[/TD]
[TD="align: right"]51[/TD]
[TD="bgcolor: #E2EFDA, align: right"]480.89[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]8[/TD]
[TD="align: right"]2[/TD]
[TD="align: right"]18[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]9[/TD]
[TD="align: right"]2[/TD]
[TD="align: right"]2[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]10[/TD]
[TD="align: right"]2[/TD]
[TD="align: right"]46[/TD]
[TD="bgcolor: #E2EFDA, align: right"]330.67[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]11[/TD]
[TD="align: right"]3[/TD]
[TD="align: right"]42[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]12[/TD]
[TD="align: right"]3[/TD]
[TD="align: right"]54[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]13[/TD]
[TD="align: right"]3[/TD]
[TD="align: right"]41[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]14[/TD]
[TD="align: right"]3[/TD]
[TD="align: right"]32[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]15[/TD]
[TD="align: right"]3[/TD]
[TD="align: right"]46[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]16[/TD]
[TD="align: right"]3[/TD]
[TD="align: right"]31[/TD]
[TD="bgcolor: #E2EFDA, align: right"]62.67[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]17[/TD]
[TD="align: right"]4[/TD]
[TD="align: right"]38[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]18[/TD]
[TD="align: right"]4[/TD]
[TD="align: right"]56[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]19[/TD]
[TD="align: right"]4[/TD]
[TD="align: right"]21[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]20[/TD]
[TD="align: right"]4[/TD]
[TD="align: right"]2[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]21[/TD]
[TD="align: right"]4[/TD]
[TD="align: right"]60[/TD]
[TD="bgcolor: #E2EFDA, align: right"]471.84[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
</tbody>
If entered correctly, Excel will surround with curly braces {}.