00:01
The mean and standard deviation of 10 observations are 20 and 8 respectively.
00:10
But later on it was observed that one of the observations was recorded as 50 when it should have been 40.
00:21
So correcting our mean isn't so tough because we can correct our mean by taking 20 times 10, subtracting that difference, and then dividing by 10 again so that we get that new mean of 19.
00:41
The standard deviation is a little bit more challenging.
00:45
So if we take 8 and set it equal to the square root of, and i'm just going to think of almost like a placeholder, the sum of the 9 values, so i'm just going to write that as the square of those 9 other values, plus 50 squared minus the square of that mean of 20 that i thought i had, and then i divided by 10.
01:28
And then i'm going to work backwards.
01:30
So the first thing i'm going to do is i'm going to get rid of the radical by squaring both sides.
01:58
Oops, that should be 4 ,000.
01:59
20 times 20.
02:06
Oh, i'm sorry, no it shouldn't be...