Which Test, and Why?

For each scenario name the appropriate test, state the null hypothesis, and give the key assumption you would check.

1. 1,200 users were shown design A and 1,180 design B; you compare click-through counts.
2. 25 sales reps each ran a demo with the old script and, a week later, with the new script; you compare their conversion percentages.
3. Response latency (ms) for two backend versions, 40 requests each; the distributions are heavily right-skewed with a few 10-second outliers, and the team cares about typical latency.
4. You want to know whether ticket category (5 categories) is related to which of 3 support channels a customer used, from a table of 2,000 tickets.
5. Which of these would you additionally analyse with a bootstrap, and for what quantity?