00:01
So the quality control manager wants to know whether the mean life of a large shipment of light bulbs is equal to 7463.
00:14
So this is our null hypothesis.
00:18
And then our alternative hypothesis is that the mean is not equal to 7463.
00:25
We have a random sample of 64 light bulbs with a sample mean of 7438.
00:35
And we're told that the standard deviation for the population is equal to 100.
00:41
And then our alpha is given to be 0 .05.
00:48
Our test statistic is x bar minus the null hypothesis mean divided by sigma over the square root of n.
00:59
So this is going to be 7438 minus 7463 divided by 100 over the square root of 64.
01:11
And that is equal to, let's see here, numerator is 7438 minus 7463 negative 25 divided by 100 over 8.
01:28
So negative 25 divided by 12 .5 is equal to negative 2.
01:42
And then the p -value is equal to the probability that z has an absolute value greater than or equal to absolute value of negative 2.
01:55
That is 2 times the probability that z is greater than or equal to 2.
02:01
That is 2 times 0 .0228, which is 0 .0456.
02:20
So since p -value is less than alpha, which is 0 .05, we reject the null hypothesis.
02:34
There is sufficient evidence to suggest that the mean is not equal to 7463.
03:04
Okay, and here's your p -value.
03:17
This was our test statistic.
03:20
That was the p -value...