20070201
¯ x ...................................mean of sample
x
σ
n -1 ............................. sample standard deviation ( x
σ
n -1 > 0)
n .................................. size of sample (positive integer)
After setting all the parameters, use c to move the highlighting to “Execute” and then press
the function key shown below to perform the calculation.
• 1 (CALC) ... Performs the calculation.
Calculation Result Output Example
Left ............................... confi dence interval lower limit (left edge)
Right .............................confi dence interval upper limit (right edge)
o ...................................mean of sample
x
σ
n -1 ............................. sample standard deviation
n .................................. size of sample
u 2-Sample t Interval
2-Sample t Interval calculates the confi dence interval for the difference between two
population means when both population standard deviations are unknown. The
t interval is
applied to
t distribution.
The following confi dence interval applies when pooling is in effect.
α
is the level of
signifi cance. The value 100 (1 – α ) % is the confi dence level.
Left = (o
1
– o
2
)– t
α
2
ight = (o
1
– o
2
)+ t
α
2
n
1
+n
2
–2
n
1
1
+
n
2
1
x
p
n–1
2
σ
n
1
+n
2
–2
n
1
1
+
n
2
1
x
p
n–1
2
σ
Left = (o
1
– o
2
)– t
α
2
ight = (o
1
– o
2
)+ t
α
2
n
1
+n
2
–2
n
1
1
+
n
2
1
x
p
n–1
2
σ
n
1
+n
2
–2
n
1
1
+
n
2
1
x
p
n–1
2
σ
x
p n–1
=
σ
n
1
+ n
2
– 2
(n
1
–1)x
1
n–1
2
+(n
2
–1)x
2
n–1
2
σ
σ
x
p n–1
=
σ
n
1
+ n
2
– 2
(n
1
–1)x
1
n–1
2
+(n
2
–1)x
2
n–1
2
σ
σ
6-6-9
Confi dence Interval
