Calculate Probit Confidence Interval By Hand

Calculating the probit confidence interval by hand is a crucial statistical technique used to estimate the range within which the true population parameter lies with a certain degree of confidence.

1. Enter the sample size.
2. Select the significance level (α).
3. Enter the probit value.
4. Click ‘Calculate’.

The formula for calculating the probit confidence interval is:

Probit Confidence Interval = Probit Value ± (Z * Standard Error)

Where Z is the critical value corresponding to the chosen significance level, and the standard error is calculated as:

Standard Error = √[(1 - Probit Value) * Probit Value / Sample Size]

Comparison of Probit Values

Sample Size	Probit Value (α = 0.05)	Probit Value (α = 0.01)
10	1.645	2.326
20	1.753	2.533

• Always use the appropriate significance level based on your study’s requirements.
• Ensure your sample size is large enough to provide a reliable estimate.
• Consider using software or calculators for complex calculations.

What is a probit value?

A probit value is the inverse of the standard normal cumulative distribution function (CDF). It’s used to transform probabilities into values that can be analyzed using linear regression.

For more information, see the following authoritative sources:

• CDC – Probit Calculator
• UCLA – Probit Regression