# Question about what this variance value means

1. Sep 1, 2009

### yopy

i calculated the variance of a few measurements and i got the value of 3.65

i know the variance tells us the degree of dispersion from them ean value, and i came up with 3.65, what does this number say about the data?

2. Sep 1, 2009

### Staff: Mentor

If you're dealing with a normal distribution, it tells you that about 69% of your values are within +/- 3.65 units of the mean.

3. Sep 1, 2009

thank you

4. Sep 3, 2009

### mathie.girl

I thought that in a normal distribution, 69% of your values are within +/- one standard deviation of the mean. So in this case, 68-69% of the data will be in the interval between $$\mu - \sqrt{3.65}$$ and $$\mu + \sqrt{3.65}$$, if your mean is $$\mu$$.

Variance is the average of the squares of the distance between your data and the mean. Like standard deviation, it also measures how spread out your data is.

5. Sep 3, 2009

### Staff: Mentor

Thanks for the correction. The (population) variance is the square of the (population) standard deviation.