televisions In of 6/ months, with a standard deviation of 7.2 months. What length of warranty should be offered, if the manufacturer wants to repair less than 1% of the televisions under the warranty? 18. A tutor guarantees that 10% of her students will obtain an A on every test they write. For the last test, the mean mark is 68 and the standard deviation is 6. What mark is required to receive an A on the test