The weights of bats in a zoo are normally distributed with a mean of 2.2 pounds and a standard deviation of 0.3 pounds. About what percent of the bats at the zoo weigh between 1.9 pounds and 2.5 pounds?

a. 34%

b. 47.5%

c. 81.5%

d. 68%
I have no clue on this one... can you please help and explain? I am COMPLETELY lost on this one this time! lol

Question

The weights of bats in a zoo are normally distributed with a mean of 2.2 pounds and a standard deviation of 0.3 pounds. About what percent of the bats at the zoo weigh between 1.9 pounds and 2.5 pounds?

     a.  34%

       b. 47.5%

       c. 81.5%

       d. 68%
I have no clue on this one... can you please help and explain? I am COMPLETELY lost on this one this time! lol

jim_thompson5910 · Answer

Have you heard of the empirical rule?

anonymous · Answer

nope... haha

jim_thompson5910 · Answer

The empirical rule says that roughly 68% of the distribution is within one standard deviation of the mean

anonymous · Answer

so the answer is automatically 68% because of that??

anonymous · Answer

or no??

anonymous · Answer

i'm still confused =(

anonymous · Answer

Note that 1.9 = 2.2 -0.3 and 2.5 = 2.2+0.3

They are in the range of 1 standard deviation.

|dw:1338369596401:dw|

The left line indicates the 1.9 point.
The middle line is the mean and is the 2.2 point
the right line is the 2.5 point.

in a normal distribution curve it is a rule that for the area between the left and right line is 68.2% 

The left and right line is found by subtracting the standard deviation from the mean and adding the standard deviation to the mean.