We formulate the null and alternative hypothesis here to state that battery life of the laptop lasts at least 12 hours(more than but not less, null hypothesis) or that it lasts less than 12 hours(alternative hypothesis).
The null hypothesis is the one being tested to know whether we would reject it or not in which case we choose the alternative hypothesis. To test the hypotheses, we do a t test using a significance level of say 0.05(95% confidence interval) and find our p value in order to compare and decide if the null hypothesis would be rejected or not based on statistical significance.
