Let’s apply this to other situations!
The mean IQ on the Stanford-Binet IQ test is 100. The Standard Deviation is 16. Thus 68.26% of people have scores between 84 and 116.

The mean of the SAT-V is 550 and the SD is 100. Thus 68.26% have scores between 450 and 650.

One college reports its SAT-V mean has 600 and its SD is at 50. Another reports it as a mean of 500 and an SD of 100. You know that the first school is higher and less variable than the second is.

Additional things to know:

• When you calculate the SD deviation from a sample (rather than a population) you divide by N –1 rather than N because sample SDs tend to be too small.
  
  
• The variance is useful later in comparing groups.
  
  
• If you have non-normal distributions, you might have to use the range and the median to summarize the central tendency and variability of the distribution.