Question 47667
The average weight of a box at a store is 10lbs. with a standard deviation of 2 lbs. If 200 boxes are at the store approximately how many boxes will be between 10 and 13 lbs.
10 AND 13 CORRESPOND TO A DEVIATION OF +3 FROM MEAN OF 10 SINCE 13=10+3
DEVIATION OF 3 IS 1.5 TIMES THE STANDARD DEVIATION OF 2 SINCE 2*1.5=3
FROM NORMAL DISTRIBUTION IT IS EXPECTED THAT ABOUT 86% WILL BE BETWEEN -1.5 S.D TO +1.5 S.D AROUND THE MEAN 
THAT IS 86% ARE BETWEEN 10-3=7 AND 10+3=13...OR..43% WILL BE BETWEEN 10 AND 13
HENCE APPROXIMATELY 200*43/100=86 BOXES MAY BE BETWEEN 10 AND 13 LBS.