This calculator will compute the confidence interval for a proportion with given sample size, number of successes, and confidence level. It will provide confidence intervals calculated using different methods, including the Normal approximation method, Wilson Score method, and Clopper-Pearson method.
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Confidence Interval for One Proportion with Normal Approximation
Definition: A confidence interval for a proportion provides a range of values that is likely to contain the true population proportion with a certain level of confidence.
Where:
- is the sample proportion
- is the critical value from the standard normal distribution
- is the sample size
Suppose in a sample of 200 people, 30 are left-handed. To calculate a 95% confidence interval:
We can be 95% confident that the true proportion of left-handed people in the population is between 10% and 20%.
Interpretation
Interpretation: We are 95% confident that the true population proportion lies within the calculated confidence interval.