The only way to compare different camera battery life is for everyone to follow a standard.
That standard has a set pattern of what is done and for how long.
It can not answer all of the possibilities and variants that anyone can imagine.
So there is no answer to the questions you asked.
If you really want to get into the nitty gritty of the formula used you can look here:
When a compact digital camera ( US $250 to 400 ) said Battery life is 200 shots , is that 200 shots with or without flash ? If w/out flash ,around how many shots with flash ? Also what would be the equivalent in terms video recording time at 720 & 1080 p with and w/out flash with time measured in minutes.
For example Digital camera said to have battery life of 200 shots is :
Battery life 200 shots is 130 shots if with flash . For video 720p wi/out flash is 30 mins , w/ flash is 20 minutes. If 1080 P w/out flash is 10 mins , w/fash 5 minutes.
Is it true that 2 same camera, one touchscreen and the other not, the touch screen drains battery more by about 15 %