00:01
So we have a mean and a standard deviation for a distribution, but we don't know the shape.
00:05
If it was a normal distribution, we'd have one way to do this, but we're going to use chebyshev's theorem.
00:11
And so we want to find what k is so that there are at least 50 % of the scores are within k standard deviations from the mean.
00:19
So i drew my little picture and i have the 0 .5 in here.
00:22
And chebyshev says that 1 minus 1 over k, where this is the number of standard deviations that we're moving away from the mean, that 1 minus 1 over k squared is equal to that area inside here, and so minimally.
00:45
So solving this, we subtract 1 half, move this to the other side, and do some manipulation.
00:52
And so k is the square root of 2, or approximately 1 .414...