The sample size should be 73.
We use the formula
To find the z-score:
Convert 95% to a decimal: 0.95
Subtract from 1: 1-0.95 = 0.05
Divide by 2: 0.05/2 = 0.025
Subtract from 1: 1-0.025 = 0.975
Using a z-table (http://www.z-table.com) we see that this value goes with a z-score of 1.96. Using this, our value for σ and our margin of error, we have:
-16+-x/4=-3
-x/4=13
-x=52
x=-52
Solve for the first variable in one of the equations, then substitute the result into the other equation.
Point Form:
(
0
,
−
6
)
(
0
,
-
6
)
Equation Form:
x
=
0
,
y
=
−
6