Testing pH Levels

Today in science we had to bring in three liquids, two liquids of choice and water.  We tested their pH levels with pH paper strips.  We had to test 15 liquids total in class.  After we collected the ph levels for all the 15 liquids.  We tested the ph levels on the probe with the same liquids and compared the ph levels to the ones we found with the ph paper strips.  For example I tested whey with the pH strip and got 6.  When I tested the whey with the probe I got about 6.