13-30 Inferential Statistics and Distributions
8313INFE.DOC TI-83 international English Bob Fedorisko Revised: 02/19/01 12:47 PM Printed: 02/19/01 1:38 PM
Page 30 of 36
normalcdf( computes the normal distribution probability
between lowerbound and upperbound for the specified
mean
m
and standard deviation
s
. The defaults are
m
=0
and
s
=1.
normalcdf(lowerbound,upperbound[,
m
,
s
])
invNorm( computes the inverse cumulative normal
distribution function for a given area under the normal
distribution curve specified by mean
m
and standard
deviation
s
. It calculates the x value associated with an
area to the left of the x value. 0 area 1 must be true.
The defaults are
m
=0 and
s
=1.
invNorm(area[,
m
,
s
])
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:
fx df
df
xdf
df
df
() [( ) ]
()
()
()
=++
−+
Γ
Γ
12
2
1212
/
/
//
π
tpdf(x,df)
Note: For this example,
Xmin = L4.5
Xmax = 4.5
Ymin = 0
Ymax = .4
normalcdf(
invNorm(
tpdf(