Backtesting not consistent

[Arun Kokate-1757655088147]

1. When I am backtesting NSE 500 index and NSE 500 50 25 25 index, the results varying a lot. The constituents of both the indices are same then why this should happen?

2. I back tested the strategies given in Prashant Shah sirs book but the results are not matching

Need guidance as I want to start my investment based on backtesting.

Thanks
RAK