Casio CLASSPAD 330 3.04 - Manual (Page 443)

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7-10-1
Confidence Intervals
7-10 Confidence Intervals
A confidence interval is a range of values that has a specified probability of containing the
parameter being estimated.
A confidence interval that is too broad makes it difficult to get an idea of where the parameter
(actual value) is located. A narrow confidence interval, on the other hand, limits the
parameter range and makes it possible to obtain highly accurate results.
The commonly used confidence levels are 68%, 95% and 99%. Raising the confidence
level broadens the confidence interval. Conversely, lowering the confidence level narrows
the confidence interval, but it also creates the risk that parameters will be missed. With a
confidence interval of 95%, for example, there is a 5% probability that a parameter will not be
within the interval.
The following is a list of confidence intervals and a description of what each obtains.
I General Confidence Interval Precautions
If you input a C-Level (confidence level) value in the range of 0  C-Level < 1, the value you
input is used. To specify a C-Level of 95%, for example, input “0.95”.
1-Sample Z Interval
Confidence Interval Name
Calculates the confidence interval for the population mean based on
a sample mean and known population standard deviation.
Z Confidence Interval
t Confidence Interval
Description
2-Sample Z Interval
Calculates the confidence interval for the difference between
population means based on the difference between sample means
when the population standard deviations are known.
Calculates the confidence interval for the population proportion
based on a single sample proportion.
1-Prop Z Interval
2-Prop Z Interval
Calculates the confidence interval for the difference between
population proportions based on the difference between two sample
proportions.
1-Sample t Interval
Calculates the confidence interval for the population mean based on
a sample mean and a sample standard deviation when the
population standard deviation is not known.
2-Sample t Interval
Calculates the confidence interval for the difference between
population means based on the difference between sample means
and sample standard deviations when the population standard
deviations are not known.