00:01
Okay, what we're going to do is kind of walk through a problem dealing with what is called systolic blood pressure.
00:14
The key component is that we know that it follows a normal distribution curve, which is super important.
00:26
Okay.
00:28
And so we are asked, well, let me backtrack.
00:34
It follows a normal distribution curve with a mean equal to 135 millimeters and a standard deviation of 16 millimeters.
00:46
Okay.
00:47
And we're asked to determine the z score of people with blood pressures of 130 millimeters and 140 millimeters.
01:01
But the critical thing is a z score is actually calculated from the data value, minus the mean over the standard deviation.
01:10
That's how we calculate a z score.
01:13
So we should be able to calculate the z score for somebody that has, so the z for somebody that has 130 is 130, minus the mean, which is the 135, divided by the standard deviation.
01:31
And so once we do that, 130 minus 135, and we're going to divide that, and remember, if you're putting this all -inclusive, put your entire numerator in parentheses and divide by 16.
01:45
And so that tells me that is negative point 3125.
01:51
The negative sign means that this is about 0 .3125 standard deviations below the mean.
02:10
Okay, the negative sign means that is below the mean.
02:15
So which we can kind of tell because if we actually draw that normal distribution curve and we put the mean right in the middle, one standard deviations below would be 135 minus 16, which would give me 119.
02:35
And one standard deviation above the mean would be 135 plus 16.
02:41
So that would be 151, right? and this is blood pressure in millimeters...
