Most pools (from my observations, note this may be very outdated now that pools have vardiff) display miner hash rates as either a 15 minute or 1 hour average. Some use slightly different windows. BTC Guild for example uses a variable window based on available data, starting with just 2 minutes worth of shares, and extending up to a full hour [and then the graphs page can give you 4-hour average hash rates].
However, hourly variance *shouldn't* mean much to a miner. Most pools have vardiff configured in a way the leads to a ~1% +/- variance on the miner's share submissions over the course of a day assuming you're mining at a point where vardiff is needed. In comparison, most GPU miners are seeing only ~6 shares per minute from a 420 MH/s GPU, which is a ~2% +/- miner variance in 24 hours.
Obviously you're still at the mercy of pool variance for non-PPS mining as well.
However, hourly variance *shouldn't* mean much to a miner. Most pools have vardiff configured in a way the leads to a ~1% +/- variance on the miner's share submissions over the course of a day assuming you're mining at a point where vardiff is needed. In comparison, most GPU miners are seeing only ~6 shares per minute from a 420 MH/s GPU, which is a ~2% +/- miner variance in 24 hours.
Obviously you're still at the mercy of pool variance for non-PPS mining as well.
The tricky thing this guy wants to do though is figure out if his miner is starting to fail. In this case the daily average is too late - he needs something that will let him know, real time, whether or not his submission rate is falling outside a particular confidence interval. So he needs to find out how many shares he's submitting (on average) in the time during which the hashrate is being averaged. As soon as the average hashrate drops lower than the calculated confidence interval, he'd get an alert.
