Answer:
The 85% confidence interval is (0.2187, 0.2613).
Step-by-step explanation:
We have a large sample of size n = 830 Americans over 45. We have observed that 631 people don't smoke. Let p be the population proportion of Americans over 45 who smoke. An point estimate of p is 
and an estimate of the standard deviation of 
is 
= 0.0148. Therefore, because we have a large sample, the 85% confidence interval for the population proportion is given by 
where 
is the 7.5th quantile of the standard normal distribution, i.e., -1.4395. Therefore the 85% confidence interval is 
or equivalently (0.2187, 0.2613).
Answer:
Cool. Carlos is a genius.
There are two ways to solve system of equations.
1) substitution method
2) elimination method
4x - y = -6
x - 2y = -5
For thus problem, i'll be using the substitute method.
So, using the equation x - 2y = -5:
Solve for "x" by adding 2y to both sides of the equation.
x = 2y - 5
Now we know what "x" is, we can substitute it in the other equation.
4x - y = -6
4(2y - 5) - y = -6
8y - 20 - y = -6
7y - 20 = -6
7y = 14
y = 2
We now know the numerical value of y. So, all we have to do is plug in y into either system of equation to solve for the numerical value of x.
4x - 2 = -6 x - 2y = -5
4x = -4 x - 2(2) = -5
x = -1 x - 4 = -5
x = -1
The solution is (-1, 2) where x equals -1 and y equals 2.
