How do I calculate confidence intervals for proportions?

How do I calculate confidence intervals for proportions?

To calculate a confidence interval for a proportion, you can use the formula: CI = p ± Z * √(p(1-p)/n), where p is the sample proportion, Z is the Z-score for your desired confidence level, and n is the sample size.

What is the Z-score for a 95% confidence level?

The Z-score for a 95% confidence level is approximately 1.96.

Can you give me an example with numbers?

Sure! If you have a sample of 100 people and 60 of them prefer product A, the sample proportion p is 0.6. The confidence interval would be calculated as follows: CI = 0.6 ± 1.96 * √(0.6(1-0.6)/100). This results in a confidence interval of approximately (0.52, 0.68).

What if my sample size is smaller?

If your sample size is smaller, the confidence interval will be wider, reflecting more uncertainty. You can still use the same formula, but be cautious with small samples as they may not represent the population well.