Measuring Usability
Quantitative Usability, Statistics & Six Sigma by Jeff Sauro

Confidence Interval Comparison Calculator

Download an Excel worksheet which calculates the four most common binomial confidence intervals with the detailed calculations.
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    $21.99     Now :  

If you will be making copies or distributing the product, please purchase the site license

Features & Benefits

  • Computes the Adjusted-Wald, Wald, Exact and Score confidence intervals
  • Easily integrate the formulas into your spreadsheets
  • Specify any confidence level (e.g. 95%, 99%, 98%)
  • Supports both 1 and 2 Tailed Confidence Intervals
  • Provides both methods for computing a confidence interval when there are all successes or all failures. One method uses 1 -tailed critical value and the other uses a 2-tailed critical value.

Who Should Buy

Those who need a quick way to compute multiple binomial confidence intervals and to have access to the formulas in Excel.

Select Sample Screen Shots

Confidence Interval Comparsions

Confidence Interval Comparsions

Easily enter the number of successes and number of failures

See the Detailed Calculations

See the Detailed Calculations

If you need to see how the Exact, Wald, Adjusted-Wald or Score intervals are calculated or want to integrate the formulas into your sheets, having the calculations is essential.

Shows both calculations where there are all successes or all failures

Shows both calculations where there are all successes or all failures

When there are all successes or all failures (for example 10/10) and you want a 95% 2-tailed confidence interval, you have a problem. A 2-tailed confidence interval means there is 1-(alpha/2) chance of the population being below the lower bound or above the upper bound of the interval. Since it is impossible to have anything above 1 (or 100%) you end up with a 97.5% confidence interval. Some calculators compensate for this by adjusting the confidence level to 90% so there is still a 5% chance of the proportion falling below the lower bound (instead of a 97.5% chance).

There is some controversy over what the "correct' approach is. Without the adjustment, you will be overstating the width of the interval. With the adjustment you will understate the width under some conditions. This calculator provides both methods.

Batch Confidence Intervals (Adjusted-Wald)

Batch Confidence Intervals (Adjusted-Wald)

If you've ever needed to compute a lot of confidence intervals fast, the batch functionality will come in handy. Just enter the number of successes and total number tested and copy formulas in excel. There's even a graph that will automatically update for you.

Batch Confidence Intervals (Exact)

Batch Confidence Intervals (Exact)

While the adjusted-wald interval is the best all-around confidence interval, there may be times where you need the exact interval (such as in medical studies when you need to be absolutely certain the confidence interval coverage is at least 95%). Simply enter the number of successes and total tested for as many rows as you need.

Binomial Confidence Intervals

  • Wald
  • Adjusted-Wald
  • Exact (Clopper-Pearson)
  • Score (Wilson Interval)

What Customers are Saying:

The confidence interval calculator is a great product. The batch feature that allows calculation of many CIs at once is a tremendous time saver. Many statistical packages still focus on statistical tests and do not calculate interval estimates, so this program fills an important gap.

Polly Bijur Ph.D MPH
Professor of Emergency Medicine, Epidemiology and Population Health Albert Einstein College of Medicine
I like the overall calculator functions and found it to be useful.

TG
Orbital Science Corp.
I needed to know how to perform a statistical test in Excel but could not figure it out. This calculator gave me exactly what I was looking for.

Sharon Kaiser


    $21.99     Now :  

If you will be making copies or distributing the product, please purchase the site license All major credit cards, debit cards and PayPal Accepted.
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