p value

The p value shows how well the data fit the assumption that there is truly no difference. A small p value means they fit poorly.

Example: p = .005. If there were truly no difference between "phone in bed: yes" and "no", a difference at least this large would turn up in only about 5 of 1,000 samples.

Caution: The p value is not the probability that the result is due to chance. It also says nothing about how large or important a difference is - that is what effect size is for.