a.) What does “p < .05” mean? b.) What is the difference between “p < .05” and “p < .01”? When would you use p < .01 rather than p < .05? Thank you in advance!! Solution a) p < .05 means that the probability is less than 5%. b) p < .01 indicates a stricter requirement. If you want to be more confident in the probability of some conclusion, then you would choose p < .01..