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Chapter 83: Sample Size for Proportions

Sample Size for Proportions
Sample size for proportions
Introduction

Researchers are frequently concerned with determining sample size for problems involving estimating population proportions or percentages. When the sample size question involves the estimation of a proportion, the researcher requires some knowledge of the logic for determining a confidence interval around a sample proportion estimation (p) of the population proportion (π). For a confidence interval to be constructed around the sample proportion (p), an estimate of the standard error of the proportion (Sp) must be calculated and a confidence level specified.

Key Features and Examples

The precision of the estimate is indicated by the value ZciSp. Thus, the plus or minus estimate of the population proportion is If the researcher selects a 95% probability for the confidence interval, Zci will equal 1.96.

The ... 