Question

For a bell curve with mean 7 and standard deviation 3, how much area is under the curve, above the horizontal axis, and between x = 2.5 and x = 11.5?

Answer 1

86,64%

Explanation:

your normalized standard deviation is 1,5 because `sigma= (7-2.5)/3= 1.5` and also `sigma= (11.5-7)/3=1.5`.
In the table you find on the line -1,5 and on the first column the value 0,0668 that means that 6,68% of the values are before 2.5 and since the distribution is simmetric it is the same also for values over 11,5
so between your valus there are 100%-2(6,68%) = 86.64% of values,