Casio ALGEBRA FX2.0 Advanced Statistics Examples 2 - Manual (Page 4)

29
examples
○ ○ ○ ○ ○
Example Construct a 94% confidence interval for the difference between the
mean lifetimes of two kinds of light bulbs(
µ
1
-
µ
2
), given that random
sample of 40 light bulbs of the first kind lasted on the average for 418
hours of continuous use and 50 light bulbs of the second kind lasted
on the average for 402 hours of continuous use. The population
standard deviations are known to be
σ
1
= 26 and
σ
2
= 22.
Procedure
1 m STAT2
2 4 (INTR) b (Z) c (2-Smpl)
3 2 (VAR) c
.je w
cg w
cc w
ebi w
ea w
eac w
fa w
1 (None) c
4 1 (CALC)
Result Screen
Thus, the 94% confidence interval for
µ
1
-
µ
2
becomes 6.3<
µ
1
-
µ
2
<25.7.