Sum of Averages in Excel Pivot Table

Question

I am measuring room utilization (time used/time available) from a data dump. Each row contains the available time for the day and the time used for a particular case. The image is a simplified version of the data.

If you read the yellow and green highlights (Room 1):

• In room 1, there are 200 available minutes on 1/1/2016.
• Case 1 took 60 minutes, case 2 took 50 minutes.
• There are 500 available minutes on 1/2/2016, and only one case occurred that day, using 350 minutes.

Room 1 utilization = (60 + 50 + 350)/(200 + 500)

The problem with summing the available time is that it double counts the 200 minutes for 1/1/2016, giving: Utilization = (60+50+350)/(200+200+500)

There are hundreds of rows in this data (and there will be multiple data dumps of differing #'s of rows) with multiple cases occurring each day. I am trying to use a pivot table, but I cannot obtain the 'sum of averages' for a particular room (see image). I am using a macro to pull the numbers out of the grand total column.

Is this possible? Do you see another way to obtain utilization? (note: there are lots of other columns in the data, like case start, case end, day of week, etc, that are not used in this calculation but are available)

Answer 1

The reason that you're getting 300 for both Average of Available Time columns is because the grand total is a grand total based on the overall average and not a sum of the averages.

• Room 1: 200 + 200 + 500 / 3 = 300
• Room 2: 300 + 300 + 300 / 3 = 300

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I could not comment on the original question, so my solution is based on a few assumptions.

Assumption #1: The data will always be grouped. EG All cases in room 1 on a given day will grouped in sequential rows.

Assumption #2: The available time column is a single value for the whole day, there will never be differing available times on the same day.

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Solution : Use column E as the Actual Available Time. This column will use a formula to determine if the current row has a unique combination (Date + Room + Available Time) to the previous and if so, the cell will contain that row's available time.

Formula to use in E2:

=IF(AND($A1 = $A2, $B1 = $B2, $C1 = $C2), 0, $C2)

Extend the formula as far down as necessary and then include the new column in your PivotTable data range.

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End Result

Answer 2

I created a unique reference by combining columns and then used sumif/countif/countif.

So the formula in column E would be: =sumif(colB,cellB,ColC)/Countif(colB,cellE)/Countif(colB,cellE)

Doesn't matter if the data is in order or not then.

Extend the formula as far down as necessary and then include the new column in your PivotTable data range.

Answer 3

The easiest method I would recommend is this.

=SUM(H:H)-GETPIVOTDATA("Average of Available Time",$G$3)

The first term sums the H column, and the second term subtracts the grand total value. It is a dynamic solution, and will change to fit the size of the pivot table.

My assumptions are that the Pivot Table was originally placed in cell G3.