In: Math
IQ scores have a mean of 100 and standard deviation of 15:
a) What percentage of scores fall between 100 & 135?
b) What percentage of scores fall between 88 & 100?
a) What percentage of scores fall between 100 & 135?
X: IQ score
We apply Z score formula
Now we use TI-83/84 calclator
Follow the path of TI - 83\84
Press " 2ND " ........> Press " VARS" ..........>select "normalcdf"
Lower : 0 ( lower value of Z score )
Upper : 2.333333333
( because Z score follows normal distribution with mean 0 and standard deviation 1 )
Now convert that area into percentage .
Percentage of scores fall between 100 & 135 =
0.490184671 * 100 = 49.01846714 %
Here we have not mention any rounding
b) What percentage of scores fall between 88 & 100?
Follow the path of TI - 83\84
Press " 2ND " ........> Press " VARS" ..........>select "normalcdf"
Lower : (-) 0.8 (Note for (-) sign select the sign which is below 3 number key on TI - 84\83)
Upper : 0
Final answer :-
percentage of scores fall between 88 & 100 = 0.2881446669 * 100 = 28.81446669 %
percentage of scores fall between 88 & 100 = 28.81446669 %
Final answer :-
a )
Percentage of scores fall between 100 & 135 = 49.01846714 %
b )
percentage of scores fall between 88 & 100 = 28.81446669 %