00:01
Okay, so we're given this hypothesis test and we're asked to use a critical value approach to come to a conclusion of a certain observed data values.
00:10
So the first step is just to find the critical value.
00:13
So what this means is that we want to find a value of z alpha so that probability observing a more extreme value test statistic than z alpha is equal to 0 .05 because 0 .05 is at p value.
00:26
And in this case, a more extreme means that z will be strictly greater than z alpha because our alternative hypothesis involves the mean being strictly greater than 50.
00:38
So if you go to your normal tables, you can find out what this is because z is just normally distributed with mean zero and variance one.
00:47
So if you look up minus 1 .96 in the normal tables, you'll see that the probability of being less and that is equal to roughly 0 .05.
00:59
So by symmetry, this means if we take plus 1 .6, instead, then the probability of being more than that is also 0 .05.
01:06
So this means that our critical value is equal to 1 .6.
01:10
So then if you want to use a critical value approach, it means that for each of the three cases, we have to compute what z is and decide whether it's more or less extreme than the critical value of 1 .6.
01:22
So let's do that.
01:24
Ok, so just to remind you, so, so we can plug in x into our formula for z...