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3. Z-INT: 1 p.: Single sample confidence interval for the proportion, p, for
large samples with unknown population variance.
4. Z-INT: p
1−
p
2
.: Confidence interval for the difference of two proportions,
p
1
-p
2
, for large samples with unknown population variances.
5. T-INT: 1
µ
.: Single sample confidence interval for the population mean,
µ
, for small samples with unknown population variance.
6. T-INT:
µ1−µ2
.: Confidence interval for the difference of the population
means,
µ
1
-
µ
2
, for small samples with unknown population variances.
Example 1 – Determine the centered confidence interval for the mean of a
population if a sample of 60 elements indicate that the mean value of the
sample is
x = 23.2, and its standard deviation is s = 5.2. Use
α
= 0.05.
The confidence level is C = 1-
α
= 0.95.
Select case 1 from the menu shown above by pressing
@@@OK@@@
. Enter the values
required in the input form as shown:
Press
@HELP
to obtain a screen explaining the meaning of the confidence
interval in terms of random numbers generated by a calculator. To scroll
down the resulting screen use the down-arrow key
˜
. Press
@@@OK@@@
when
done with the help screen. This will return you to the screen shown above.
To calculate the confidence interval, press
@@@OK@@@
. The result shown in the
calculator is:
