Unique visitors: hours vs day

Hey guys,

I’m a bit stumped on a certain piece of analytics. I’ts been really driving me nuts! Here it is…

When retrieving statistics via the API hourly, they sum up to be different than when retrieving the statistics daily.

Example: API hourly for 3-25-2012 says I had 90 unique visitors. API daily says for 3-25-2012 I had 86. Now when looking at the dashboard, the total unique visitors matches the daily API pull. However, when exporting and looking at the hourly totals, it adds up to a different number (90).

Does anyone know why there is a disparity in the numbers, I’ve actually noticed this in Google Analytics as well. I can’t figure out what the problem is, or a solution. I thought it was related to time zones but I created a matrix of several days and visitors and could not find any type of pattern, ie it being off by 2 hours or something of that nature.

Thank you for your help!
Matt

Unique visitors are unique on the day, but they will count several times per day for each hour this visitor made a visit.

If you sum “Visits” by hour it should add up with daily visits ?