Confidence Interval - Casio FX-9750G plus User Manual

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18-7 Confidence Interval

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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.
Z
1-Sample Interval calculates the confidence interval when the population
standard deviation is known.
Z
2-Sample Interval calculates the confidence interval when the population
standard deviations of two samples are known.
Z
1-Prop Interval calculates the confidence interval when the proportion is not
known.
Z
2-Prop Interval calculates the confidence interval when the proportions of two
samples are not known.
t
1-Sample Interval calculates the confidence interval for an unknown population
mean when the population standard deviation is unknown.
t
2-Sample Interval calculates the confidence interval for the difference between
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.
Z t
Z t
• { }/{ } ... { }/{
About data type specification
For some types of confidence interval calculation you can select data type using the
following menu.
• {List}/{Var} ... specifies {List data}/{parameter data}
manuals search engine
} confidence interval calculation
t Z
test and test the data, you must