type II error; false negative
In statistics, the error of failing to reject a false null hypothesis; contrasted with 第一種の過誤 (type I error).
See also: 第一種の過誤
A type II error is the mistake of concluding there is no difference when there actually is one.
With a small sample size, the probability of a type II error increases.
第一種の過誤 is a type I error (false positive), while 第二種の過誤 is a type II error (false negative).
A technical term composed of 第二種 (the second kind) + の + 過誤 (error), directly corresponding to the English statistical term 'type II error'.