Averages seem off - Fuel Economy, Hypermiling, EcoModding News and Forum

Tourigjm · 07-30-2008, 10:17 PM

I keep my own fuel log separate from the one on ecomodder. the average i calculate in my excel file is lower than the one in my log here. IDK what the difference is, but all my entries are the same. I attached my excel file maybe check the formulas? i've checked mine and i cant find the problem

(I use the latest version of office, idk what the "dumbed down" .xls file will look like

)

Noel · 07-30-2008, 10:22 PM

To what decimal do you take your excel file?

Default is 2 decimal, so it rounds,,, highlight all the cells and properties, bring it to 10 spaces if this is the problem.... for the sheet I was keeping, I had to do this to get accurate "per mile" values

MetroMPG · 07-30-2008, 10:25 PM

It looks like you're actually averaging your tank fuel economy in your spreadsheet, whereas the garage here is technically a cumulative value, not an average (ie. it sums distance traveled and divides by the sum of fuel consumed).

azraelswrd · 07-30-2008, 10:29 PM

I did what Noel suggested (though not to 10 places) on my own spreadsheet to account for the inaccuracies inherent with rounding off.

Tourigjm · 07-30-2008, 10:45 PM

10 decimal places doesn't change anything significantly
my spreadsheet says my average is 33.77
ecomodder log says 34.26
sum (total miles/total gallons) = 32.27 in excel.

difference in the ecomodder avg and the sum avg from excel is like 9%... relatively big

MetroMPG · 07-30-2008, 10:57 PM

Your spreadsheet entry for 14/05/08 has fuel volume entered, but no distance value. It's throwing off the results. Omit that value from the comparison and things line up.

Tourigjm · 07-30-2008, 10:59 PM

Quote:

Originally Posted by MetroMPG

Your spreadsheet entry for 14/05/08 has fuel volume entered, but no distance value. It's throwing off the results. Omit that value from the comparison and things line up.

touche

azraelswrd · 07-30-2008, 11:01 PM

ah, beat me to it.

MetroMPG · 07-31-2008, 02:12 PM

Now if only I could spot my own mistakes...

cfg83 · 07-31-2008, 02:37 PM

Noel -

Quote:

Originally Posted by Noel

To what decimal do you take your excel file?

Default is 2 decimal, so it rounds,,, highlight all the cells and properties, bring it to 10 spaces if this is the problem.... for the sheet I was keeping, I had to do this to get accurate "per mile" values

When you say 2 decimal, can you be more specific? It sounds (to me) like you are talking about the display format. If you mean the display format, I thought that rounding did not apply to the actual calculation.

CarloSW2