Be sure that polygon ABCD is not touching its image. Draw a line segment connecting point A and point AGH. Notice that intersect
s the line of reflection, . Mark the point of intersection of and . Measure and record the angle at the intersection of and . What happens if you move the line of reflection?
The number of people who voted follows a binomial distribution with probability of having voted and subjects, which means the approximating normal distribution should have mean and standard deviation .
and 
subjects, which means the approximating normal distribution should have mean 
and standard deviation 
.