You can, but that's not necessarily problematic in itself (perhaps slightly depending on what your aim is). By definition, using a statistical significance thre

You can, but that's not necessarily problematic in itself (perhaps slightly depending on what your aim is). By definition, using a statistical significance threshold of 0.05 means that you will have 5% false positive rate. You always expect that _some_ results are erronous (either false positive or false negatives), and the point of using p-values is merely to control the rate at which this happens. That said, you can do something called multiple comparisons corrections, where you take into account the fact that you're doing multiple tests in the same go. In this case you'll end up being more conservative, and it's not the false positive rate you'll be controlling - instead you'll control the family-wise error rate, which basically has to do with whether _any_ of your positive results are false positives.