How to calculate average fleet age? URGENT

What excel version are you using. Your profile says 97-2003, but you attached an .xlsx....

What EXACTLY are the numbers that we are looking at? Why do the totals not add up??

With a helper column (manually calculated), being the number of years in each range (e.g. 0-2 is 2; 2-5 is 3, etc) in L2 to L5.

With replacement of n/a with 0

With the assumption (there is no alterantive, I think) that the number of cars in each RANGE is evenly distributed amongst the number of years in that range: e.g. 100 cars in the 0-2 range is equivalent to 50 cars in each year

Use this array formula, copied across:

Formula:

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I have included a "proof" from row 10 downwards (for my benefit as much as yours!!).


Array Formulae are a little different from ordinary formulae in that they MUST be confirmed in the FIRST CELL ONLY by pressing CTRL+SHIFT+ENTER to activate the array, not just ENTER. After that, the array can be dragged down as normal, to cover the desired range.

You will know the array is active when you see curly brackets { } - or "curly braces" for those of you in the USA, or "flower brackets" for those of you in India - appear around the outside of your formula. If you do not use CTRL+SHIFT+ENTER you will (almost always) get an error message or an incorrect answer. Press F2 on that cell and try again.

Don't type the curly brackets yourself - it won't work...

You may need ; as the separator instead of ,

On reflection, since the number of old cars in the early years is not zero, but is unknown... it might be more valid to EXCLUDE them from the analysis altogether and use ONLY those ranges (i.e. up to 10 years) where you have a complete set of data.

But... you know why you want these numbers... so your own opinion is more important than mine!!

I've just realised. It doesn't always work. The sample gicves the correct answer only by acident. It's PROBABLY OK for your numbers... but only probably. Back to the drawing board!!

Purely by luck, the answers were correct, even though the formula was wrong!! It worked fine, providing that the estimated number of cars per year BETWEEN age groups ALWAYS FELL with incereasing age. In this case, it was the case... but it might not always be so. Two helpers, even though only one is used. the other is there to indicate the source of the numbers in the array constant ( the {0,2,5,10} towards the end of the formula) just in case your datasets don't always follow the same pattern.

The revised formua is longer (there may be a way to shorten it... but my head is now sore!!). It's still an array formula.