More detail information is available here:
If you want to stop Google from gathering this information for their other products then follow these four simple steps:
1) Sign into your Google account.
2) Go to https://www.google.com/history
3) Click "remove all Web History."
4) Click "ok"
This does not stop Google from gathering the information from gathering and storing this information, it only stops them from using it in their other products.
Click the link above for more information if interested. Just thought I would share...