Hey, can someone teach me this? i haven't been at school to learn it and i have a quiz later.

example:
the scores on the sat form a normal distribution with a mean of 500 and a standard deviation of 100.

what is the minimum score necessary to be in the top 15% of the sat scores?

find the range of values that define the middle 80% of the distribution of sat scores.

604

Step-by-step explanation:

"Top 15%" corresponds to the rightmost area under the standard normal curve to the right of the mean.  That means 85% of the area under this curve will be to the left.  Which z-score corresponds to the area 0.85 to the left?

Using a calculator (invNorm), find this z-score:  invNorm(0.85) = 1.0346.

Which raw score corresponds to this z-score?

Recall the formula for the z-score:

       x - mean

z =

         std. dev.

Here we have:

       x - 500

z = - 1.0364, or x - 500 = 103.64.  Then the minimum score

          100                necessary to be in the top 15% of the scores is

                                  found by adding 500 to both sides:

                                   x = 603.64

to determine the unit cost your would divide the total cost by the number sold.

7 bagels for $4.41       $4.41/7 = $.63 each at fresh side

5 bagels for $3.60         $3.60/5 = $.72 each at value mart