Question 610145
  <pre><font face = "Tohoma" size = 3 color = "indigo"><b> 
Hi,
 a mean score on a standardized test is 50 with a standard deviation of 10.
(a)What scores 'x' fall between -1 and +1 standard deviation? 40 < x <60
(b) What percent of all scores fall between -1 and +1 standard deviation? ~68%
(c) What scores falls at +2 standard deviations? {{{70}}}
(d)What percentage of scores falls between +1 and +2 standard deviation? 95.4-68.2 = 27.2%
<u>For the normal distribution: </u>
one  standard deviation from the mean accounts for about {{{68.2}}}% of the set 
two standard deviations from the mean account for about {{{95.4}}}%
and three standard deviations from the mean account for about {{{99.7}}}%.
{{{drawing(400,200,-5,5,-.5,1.5, graph(400,200,-5,5,-.5,1.5, exp(-x^2/2)), green(line(1,0,1,exp(-1^2/2)),line(-1,0,-1,exp(-1^2/2))),green(line(2,0,2,exp(-2^2/2)),line(-2,0,-2,exp(-2^2/2))),green(line(3,0,3,exp(-3^2/2)),line(-3,0,-3,exp(-3^2/2))),locate(4.8,-.01,z),locate(4.8,.2,z))}}}