Your sample most likely is biased, but simply getting a high number does not 100 percent mean your answer was biased. It could be a pure coincidence that you picked students with high GPAs. However, it is likely that your answer is biased. You may have sampled kids that are in advanced classes. You may have sampled students that were in some sort of honors club. You may have sampled students that were all hanging out in the library, a place that most people come to study and prepare for classes. So again, while your higher than normal answer could have been a coincidence, you most likely had a biased sample.
