It has been a while since i did statistics. the question posed is:
assume that a population of thousands of people whose responses were used to develop an anxiety test had scores that were normally distributed with m=30 and s=10. what proportion of people in this population would have anxiety scores within each of the following ranges of scores? below 20, above 30, between 10 and 50. i made my bell curve, put 30 in center of my curve, added 10 to each side and went to my z table but am wondering below 20 do i subtract 20-30 to get to the 0 on my curve or do i only minus 10 because it is also asking between 10 and 50