What is the Probability of Rejecting the Mean of 130 at the 1% Level?

[dim&dimmer]

Homework Statement

Having trouble understanding the question, which is...
voltage specified to be 130
Sample of 20 readings gives sample mean of 128.25
Also given s.d.=3.

"It is important that the voltage not be allowed to drop below 128 volts. What is the probability of rejecting mean of 130 at the 1% level if in fact the mean is 128?

Homework Equations

this is part c, already tested the hypothesis regarding the true mean and found the critical value for 1%.

The Attempt at a Solution

I think this involves bayesian methods but the language (grammar) of the question confuses me, if someone could restate it that would be great.

 

[dim&dimmer]

I have figured it out