# Chapter 9: Estimating the Value of a Parameter

Using Confidence Intervals

In Section 8.2, saw the following excerpt from a report by the Pew Research Foundation:

Hispanics See Their Situation in U.S. Deteriorating

Half (50%) of all Latinos say that the situation of Latinos in this country is worse now than it was a year ago, according to a new nationwide survey of 2,015 Hispanic adults conducted by the Pew Hispanic Center. (Source: Pew Research)

Further down that particular article, there's another interesting line:

The margin of error for the full sample is plus or minus 2.8 percentage points; for registered voters, the margin of error is 4.4 percentage points.

How did they determine that the margin was ±2.8%?

This is the question we'll answer in Chapter 9. In fact, we'll talk about confidence intervals for the population mean, population proportion, and population variance.