---
url: "https://questionstar.com/principles-of-survey-research/chapter-4/slide-141.html"
title: "Margin of Error Approach: Two Formulas"
type: "lehrbuch-slide"
chapter: 4
chapterTitle: "Sampling"
slide: 141
---

# Margin of Error Approach: Two Formulas

*The Problem of Unknown Dispersion*

![x = x̂ ± E](/principles-of-survey-research/media/formel_top.png)

x = true value of the parameter x̂ = sample value E = margin of error

For Metric Data

Means

Assessing means calculated from the sample

Usually unknown

z z-value for the specified confidence level

σ Standard deviation of the parameter in the population

n Sample size

For Proportions

Proportions

Assessing calculated proportions

Usually unknown

z z-value for the specified confidence level

π Estimate of the proportion in the population

n Sample size

---

*Slide 141 of 274 · Chapter 4: Sampling · Principles of Survey Research · Dr. Paul Marx*