Posted by nicole on .
Assume that a set of test scores is normally distributed with a mean of 80 and a standard deviation of 25. Use the 689599.7 rule to find the following quantities.
The percentage of scores less than 80 is?

statistics 
drwls,
Since 80 is the mean, the fraction le4ss than that is 50%. You don't need to invoke a 689599.7 rule to figure that out. You also don't need to know the standard deviation.