9.3 Hypothesis testing of single mean and single proportion:  (Page 4/4)

Investigated and reported by William S. Gossett in 1908 and published under the pseudonym Student. The major characteristics of the random variable (RV) are: It is continuous and assumes any real values. The pdf is symmetrical about its mean of zero. However, it is more spread out and flatter at the apex than the normal distribution. It approaches the standard normal distribution as n gets larger. There is a "family" of t distributions: every representative of the family is completely defined by the number of degrees of freedom which is one less than the number of data.