00:01
In your problem, you're dealing with assuming that the distribution is normal, so it's a bell -shaped curve, and that the battery usage is supposed to be centered at 11 .75 hours, and the standard deviation is 2 .1 hours.
00:18
But you didn't ask a question.
00:21
So if you wanted to know something, this is in normal distribution.
00:25
So let's say you wanted to have, i'll just give you a, for instance, what's the likelihood that the, battery will last longer than 13 hours.
00:38
Then you would be converting that to a z value.
00:41
You'd take your 13 minus the 11 .75 divided by the 2 .1 and get that as a z value and i'll quick put that in 13 minus 11 .75 and then divided by 2 .1.
00:58
That z value happens to come out to be a approximately 0 .60 and then you would want to find that probability and the easier thing to do would be to look up a z value that is lower than that lower than negative 0 .6 and that would give me a probability of 0 .2743 so only 27 % of the batteries if they're heavily used would last longer than 13 hours now the other thing you might want to know is what's the like what length of battery is maybe the 95th percentile or something like that.
01:45
So in a picture for that distribution above, 95 % of the time, the battery will last at least how long.
01:54
And so then we would need to look up what this number is in our table.
01:58
And we'd look up that 0 .95, and that's a very common one to come up with.
02:03
And it's approximately 1 .645, halfway between, the one is 0 .9 .945, and the other one gives me 0 .9505...