forcasting

thank you very much for your help.

I came across this question.
laspeyre index for price in 2005 with base year of 20*0 is 150.0
corresponding paache index is 138.24.

what is fishers ideal index.

I have not seen any where a mention of fishers ideal index in the lectures relating to Forcasting topic therefore I am assuming its not part of the syllabus please Advice me on this. Many thanks.