Question 143683
Since the mean is 8 oz, the answer to part a) is HALF.  That is, 50%.


For the b) part, you must draw a bell-shaped curve, and mark off three standard deviations to the left and three to the right.  Do you know what I mean by this?  Then, label the mean in the middle at 8 oz., and to the right, ADD .5 oz for each mark, and to the left SUBTRACT .5 oz.  This is what you should have, from left to right:
6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5.


Now, the "area" within 1 standard deviation of the mean represents 68% of the total area, and it is divided with half on each side of the mean.  This means that you have 34% of the area on each side.  So the number of cups that are LESS THAN 7.5 oz will be 50% - 34%=16%.


If by chance you wanted to know how many are MORE than 7.5 oz, you would have to add 34% + 50%= 84%.


A picture would be worth a thousand of these paragraph explanations, but I don't know how to do draw a bell curve in this medium.


R^2