Texas Instruments TI-83 PLUS - Manual (Page 730)

TI-83 Plus Tables and Reference Information 727
otherwise:
df
Sx n Sx n
Sx
p
2
2 2
2
1 1
) 1 ( ) 1 (
− + −
=
p
Sx
n n
S
2 1
1 1
+ =
2
2 1
− + =
n n df
and Sxp is the pooled variance.