00:01
For part a of this problem, we are being asked to find what is the probability that 12, of those 12 persons have an average reaction time greater than 180.
00:14
So we first find the c scored by subtracting 180, which is the desired value, minus 190, which is the mean, divided by 20, which is the standard deviation, and this is at the same time divided by the square root of the sample size, which is the square root of 12.
00:36
Put this into our calculators, and we get that the c scored is negative 1 .7 .3 to 1 .1.
00:46
Now that we have the c score, we can find the p value, which is the probability of x being smaller than 180.
00:55
Actually not smaller it's greater than 180 and therefore this we go to our p tables using the c scores and since we're looking for a greater value every time we do greater values we have to do right -tail test and the right -tail test gives us that the p value or the probability is 0 .9584 or 95 .84 percent now we go to part b in part b, let's see, we're being as how many people are we given? we are being 12 people again.
01:35
Actually, no, we're given 16 people for this problem, and their reaction time less than 191.
01:43
So we start by looking for the c scored, 191 minus the mean of 190 divided by 20, which is the standard deviation divided by the square root of 16.
01:58
So let's put this into our calculators and we get that this c scored is equal to 0 .2.
02:05
So now that we have the c score, we can find the p value of x being smaller than 191.
02:15
And we go to our p tables, find given a c score of 0 .2...