# Math Help - Writing a null and alternate hypothesis

1. ## Writing a null and alternate hypothesis

I am working on a confusing hypothesis test. The scenario is there is a new method to retread tires. The company wants to know if more than 85% of the tires have mileage lives above 30,000 miles.
Here's some of the calculated data I have so far: xbar = 35201, s = 2615, n = 50. The instructions preset alpha at 0.05.

How do I write this null and alternate hypothesis?

mu is greater than ???
mu is less than/equal to ???

2. FROM .......xbar = 35201, s = 2615, n = 50 ............it seems that you want to prove

$H_a:\mu>30,000$ where $\mu$ is the expected life time of these tires.

HOWEVER, the question seems to be about probabilities...

Based on the english I would say $H_a>.85" alt="H_a>.85" />

where p is the true poroprtion (probability) of tires that survive 30,000 miles.