Hi,
If I have an ad running for few hours for 3$ on popAds
these are its results:

should I kill it or make some changes and give it another try?
What can cause that one day an ad has a positive roi and a day after it got a negative one?
like in this screen shout:

and another wandering, if an ad gets no conversions for 2 days, like here:

should i give it another day, or there is no chance for it to bring results in the 3rd day?
Tnx!
Volatility in conversion rate is the name of the pop traffic game.
It looks like you were profitable on at least one day, and on the day when you were negative, it wasn't hopelessly negative.
I would definitely suggest to keep that running, and to cut placements (website IDs) that are not profitable after, say, 3-5 times the payout (e.g. if payout is $0.05, then you can blacklist/exclude all websites that have spent $0.15-0.25 but are still not profitable).
I normally recommend doing this after 2 times the payout, but for payouts this low, and on a source like PopAds where traffic volume isn't high, 3-5x sounds about right!
Yes there will be volatility - but there is usually a RANGE of ROIs the performance will waver within. The trick is to optimize the campaign to the point where OVERALL speaking you'd still be making profits. If most days you're positive but dipping into the red occasionally, it won't be the end of the world. Also, after a while, you can start dayparting - by only running the campaign during certain times of day and days of week. But in order to make that type of decisions, you'd need to collect more data first.
Amy