A county with a large population need to know what the average income is for tax purposes. A simple random sample of 1000 household reveals the following information. The average household income for the sample is $21,000. The median income of the sample is $17,000. The SD of the sample is $10,000, Q1 = $11,000 and Q3 = $24,000.
Find a 95% confidence interval for the average household income in this county
a. $21,000 \pm 1.96 \frac{\sqrt{10,000(1-\frac{10000}{1000})}}{1000}
b. $17,000 \pm 1.96 \frac{\sqrt{10,000(1-\frac{10000}{1000})}}{1000}
c. $21,000 \pm 1.96 \frac{10000}{\sqrt{1000}}
d. $17,000 \pm 1.96 \frac{10000}{\sqrt{1000}}