---
url: "https://questionstar.com/principles-of-survey-research/chapter-4/slide-151.html"
title: "Confidence Interval and Confidence Level"
type: "lehrbuch-slide"
chapter: 4
chapterTitle: "Sampling"
slide: 151
---

# Confidence Interval and Confidence Level

*An estimated range of values together with the probability that this range contains the unknown parameter value.*

Confidence interval

An estimated **range of values** together with the probability that this range contains the unknown parameter value.

Confidence level

The **expected proportion** of intervals that contain the parameter value across many samples.

Example · Working Hours

Sample of 30 people → avg. **7.5 h** . Confidence interval: **7.2 – 7.8 h** (margin of error ± 0.3).

**95% confidence level** means: if you repeated the measurement **100 times** with new samples, the true average would fall within this range in **95** of the cases.

Many samples · 95% capture μ

Each bar = one confidence interval. Red = misses the true value.

*[Diagramm: Confidence Interval and Confidence Level]*

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*Slide 151 of 274 · Chapter 4: Sampling · Principles of Survey Research · Dr. Paul Marx*