I followed the instruction of a poster, which is

http://www.pokertracker.com/repository/statistics.php

Search for Standard deviation.

Download the statistic called: "Standard Deviation Per 100 Hands"

Now go to you're PT3.
Go to: Configure >>> Configure Stats >>> Statistics.
Press the "import" button and import the file you have downloaded.

Now you should have the Standard Deviation as a Stat in PT3!

and I updated the cache. But it didn't work. And I repeat the instructions.

Anyone knows what's happening? Will what I did have any negative affect on my database?

If you imported the statistic that way, it's there, you just need to add it to reports to see it. For whichever report you want to add it to, click the little wrench icon at the top right of the report and find the stat on the left and double click to add it to the report.

I'm not sure off the top of my head what stat section standard deviation was built in; it will only work in certain reports, but I'm not sure which.

Alternately, if you can wait a few days, standard deviation for your general play will be available in the next Beta version on a page that mimics the PTv2 More Details page.

thanks