In forming a 95% confidence interval for a population mean from a sample size of 20, the number of degrees of freedom from the t-distribution equals 18.

Degrees Of Freedom

Degrees of freedom in statistics represent the number of independent values or quantities that can vary in an analysis without violating any constraints, often influencing the calculation of statistical parameters.

T-Distribution

A probability distribution that arises in the sampling distribution of sample means, especially useful when the sample size is small and the population variance is unknown.

Population Mean

The average value of all members of a defined set of people, objects, events, or values of interest.