Question 1154134
Use a normal approximation to find the probability of the indicated number of
voters. In this​ case, assume that 103 eligible voters aged​ 18-24 are randomly
selected. Suppose a previous study showed that among eligible voters aged​ 18-24,
22% of them voted.
Probability that exactly 28 voted
<pre>
{{{matrix(6,1,
n = 103,
p = 0.22,
q = 1-0.22=0.78,
mu=np=103(0.22)=22.66,
sigma=sqrt(npq)=4.204,
x=28)}}}

The desired approximation is the probability that x lies between 27.5 and 28.5,
using those values of the mean and standard deviation. 

{{{P(27.5<x<28.5)}}}

Get the z-scores for those two values and we find that it equals:

{{{P(1.15<z<1.39)}}}

That gives 0.4177-0.3749 = 0.0428

The TI-83 or TI-84 calculator gives a more accurate answer than can
be gotten through tables.  They both round to 0.04.  So 4% is about
as close as you're going to get.

Edwin</pre>