Confidence Interval - Casio CFX-9850G PLUS Calculations Manual

18 - 8

Confidence Interval

18-7 Confidence Interval
A confidence interval is a range (interval) that includes a statistical value, usually
the population mean.
A confidence interval that is too broad makes it difficult to get an idea of where the
population value (true value) is located. A narrow confidence interval, on the other
hand, limits the population value and makes it difficult to obtain reliable results.
The most commonly used confidence levels are 95% and 99%. Raising the
confidence level broadens the confidence interval, while lowering the confidence
level narrows the confidence level, but it also increases the chance of accidently
overlooking the population value. With a 95% confidence interval, for example, the
population value is not included within the resulting intervals 5% of the time.
When you plan to conduct a survey and then
also consider the sample size, confidence interval width, and confidence level.
The confidence level changes in accordance with the application.
1-Sample
standard deviation is known.
2-Sample
standard deviations of two samples are known.
1-Prop
known.
2-Prop
samples are not known.
1-Sample
mean when the population standard deviation is unknown.
2-Sample
two population means when both population standard deviations are unknown.
While the statistical data list is on the display, press 4 (INTR) to display the
confidence interval menu, which contains the following items.
About data type specification
For some types of confidence interval calculation you can select data type using the
following menu.
294
Z
Interval calculates the confidence interval when the population
Z
Interval calculates the confidence interval when the population
Z
Interval calculates the confidence interval when the proportion is not
Z
Interval calculates the confidence interval when the proportions of two
t
Interval calculates the confidence interval for an unknown population
t
Interval calculates the confidence interval for the difference between
Z t Z t
• { }/{ } ... { }/{ } confidence interval calculation
• {List}/{Var} ... specifies {List data}/{parameter data}
t Z
test and test the data, you must