Question

question 1 of 28
an 80% confidence interval is found to be (12,20). what is the margin of
error?
a. 6.4
b. 3.2
c. 4
d. 8

Explanation:

Step1: Find the sample mean

The sample mean $\bar{x}$ is the mid - point of the confidence interval. The formula for the mid - point of an interval $(a,b)$ is $\bar{x}=\frac{a + b}{2}$.
For the interval $(12,20)$, we have $\bar{x}=\frac{12 + 20}{2}=\frac{32}{2}=16$.

Step2: Calculate the margin of error

The margin of error $E$ can be found using the formula $E=\bar{x}-a$ (or $E = b-\bar{x}$).
Using $E=\bar{x}-a$, with $\bar{x}=16$ and $a = 12$, we get $E=16 - 12=4$.

Answer:

C. 4