Chapter 4 · Sampling · Slide 152/274
Confidence Interval, Margin of Error, and Sample Size
The higher the certainty (confidence probability) we need, the wider the confidence interval becomes — and the larger the margin of error.
4.4 · Sample Size
Relationship
Confidence Interval, Margin of Error, and Sample Size
The higher the certainty (confidence probability) we need, the wider the confidence interval becomes — and the larger the margin of error.
1.96
for 95%
→ margin of error ≈ 1 / √n
2.58
for 99%
→ margin of error ≈ 1.29 / √n
More certainty → larger z-value → for the same precision you need a larger sample.
95 %
99 %
QUESTIONSTAR · Dr. Paul Marx
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