User manual - Tests (TEST)
18
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u2-Sample t Test
2-Sample t Test compares the population means when standard deviations are unknown.
The 2-Sample t Test is applied to t-distribution.
t =
o
1
– o
2
x
1 n–1
2
σ
n
1
+
x
2 n–1
2
σ
n
2
o1 : mean of sample 1
o2 : mean of sample 2
x1
σ
n-1 : standard deviation of sample 1
x2
σ
n-1 : standard deviation of sample 2
n1 : size of sample 1
n2 : size of sample 2
This formula is applicable when the sample is not pooled, and the denominator is different
when the sample is pooled.
Degrees of freedom df and xp
σ
n-1 differs according to whether or not pooling is in effect.
The following applies when pooling is in effect.
df
= n1 + n2 – 2
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
The following applies when pooling is not in effect.
df =
1
C
2
n
1
–1
+
(1–C )
2
n
2
–1
C =
x
1 n–1
2
σ
n
1
+
x
2 n–1
2
σ
n
2
x
1 n–1
2
σ
n
1
Perform the following key operation from the statistical data list.
3(TEST)
c(T)
c(2-Smpl)