# Determining Confidence Intervals, - HP F2226A - 48GII Graphic Calculator User Manual

Graphing calculator.

reason to believe that the two unknown population variances are different, we
can use the following confidence interval
(
X
X
)
1
2
where the estimated standard deviation for the sum or difference is
and n, the degrees of freedom of the t variate, are calculated using the integer
value closest to
ν
=
[(
S
1
Determining confidence intervals
The application 6. Conf Interval can be accessed by using ‚Ù—
@@@OK@@@. The application offers the following options:
These options are to be interpreted as follows:
1. Z-INT: 1 µ.: Single sample confidence interval for the population mean,
µ, with known population variance, or for large samples with unknown
population variance.
2. Z-INT: µ1−µ2.: Confidence interval for the difference of the population
means, µ
- µ
, with either known population variances, or for large
1
2
samples with unknown population variances.
2
t
s
( ,
X
X
ν
,
α
2 /
1
X
±
X
1
2
2
s
s
s
=
1
+
X
±
X
n
n
1
2
1
2
2
[(
S
/
n
)
+
(
S
/
1
1
2
2
2
/
n
)
/(
n
1
)]
+
[(
S
1
1
2
2
)
t
s
2
ν
,
α
2 /
X
±
X
1
2
2
2
2
2
n
)]
2
/
n
)
/(
n
1
)]
2
2
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