Assess the impact of an event on a population. I ran a survey before the event and then I ran the survey after the event. The collected responses matched between prior to the event and after. I used paired t-test to determine if the event had a positive impact or a negative impact on the audience. Is it valid to calculate the p-value and based on the results and the averages for pre and post decide if the event had a positive impact or a negative impact? The sample size is about 60. How can I determine if I need the one tail or the two tailed test?