The mean of a normal probability distribution is 500 and the standard deviation is 10. about 95.44 percent of the observations lie between what two values?

per the 68-95-99 rule

 95 % lie within 2 standard deviations

 so 2 x 10 = 20

500-20 = 480

500+ 20 = 520

 so 95% lie between 480 and 520

1. perpendicular

2. parallel

3. perpendicular