250 minus 1, let's get our calculator out again. We have 142 times 1 minus 0.568 squared plus 108 times 0 minus 0.568 squared, and then all of that divided by 250 minus 1 is 249. Our sample variance is 0.246. If you were to take the square root of that, our actual sample standard deviation is 0.496. I'll just round that up to 0.50. That is our sample standard deviation. Let's think of it this way.