Texas Instruments TI-83 PLUS - Manual (Page 430)

TI-83 Plus Inferential Statistics and Distributions 427
tpdf(
tpdf( computes the probability density function (pdf) for the Student- t
distribution at a specified x value. df (degrees of freedom) must be >0. To
plot the Student- t distribution, paste tpdf( to the Y= editor. The probability
density function (pdf) is:
df
df x
df
df
x f
df
π
2 / ) 1 ( 2 ) / 1 (
) 2 / (
] 2 / ) 1 [(
) (
+ − +
Γ
+ Γ
=
tpdf( x , df )
Note: For this example,
Xmin = L 4.5
Xmax = 4.5
Ymin = 0
Ymax = .4
tcdf(
tcdf( computes the Student- t distribution probability between lowerbound
and upperbound for the specified df (degrees of freedom), which must be
> 0.