What is under the hood of your statistical
software?
•
Compare two normally distributed series with equal
variance:
t
=
x
1
-
x
2
s
1
2
(
1
n
1
+
1
n
2
)
m
1
-
m
2
=
x
1
-
x
2
–
s
1
2
(
1
n
1
+
1
n
2
)
t
0.975
(
df
1
+
df
2
)