6-6-7

Confidence Interval

u 2-Prop Z Interval

2-PropZ Interval uses the number of data items to calculate the confidence interval for the defference between the proportion of successes in two populations.

The following is the confidence interval. α is the level of significance. The value 100 (1 – α) % is the confidence level.

Left = x1 – x2 – Z α

n1 n2 2

Right = x1 – x2 + Z α

n1 n2 2

 

 

 

 

 

 

 

 

 

 

 

 

n1, n2

: size of sample

 

x1

x1

 

 

 

x2

 

x2

 

 

 

 

 

 

 

 

n1 1– n1

+

 

n2

1– n2

 

x1, x2

: data

 

 

n1

 

 

 

n2

 

 

 

 

 

 

 

 

 

 

 

 

 

x1

x1

 

 

x2

x2

 

 

 

 

n1

1– n1

+

n2

1– n2

 

 

 

 

 

n1

 

 

 

 

n2

 

 

 

 

 

 

 

 

 

 

 

 

 

Perform the following key operations from the statistical data list.

4(INTR)

1(Z)

4(2-P)

Data is specified using parameter specification. The following shows the meaning of each item.

C-Level ........................

confidence level (0 <C-Level < 1)

x1 .................................

data value (x1 >0) of sample 1

n1 .................................

size (positive integer) of sample 1

x2 .................................

data value (x2 >0) of sample 2

n2 .................................

size (positive integer) of sample 2

Save Res ....................

list for storage of calculation results (None or List 1 to 26)

Execute .......................

executes a calculation

After setting all the parameters, use c to move the highlighting to “Execute” and then press the function key shown below to perform the calculation.

• 1(CALC) ... Performs the calculation.

Calculation Result Output Example

20050401