Statistics Dictionary
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Degrees of Freedom
The number of degrees of freedom generally refers to the number of independent
observations in a sample minus the number of population parameters that must be
estimated from sample data.
For example, the exact shape of a
t distribution
is determined by its degrees of freedom. When the t
distribution is used to compute a
confidence interval
for a mean score,
one population parameter (the mean) is estimated from sample
data. Therefore, the number of degrees of freedom is equal to the sample size
minus one.
