Casio CLASSPAD330PLUS Lower = (o1, sp2, sp2, sx22, sx12, sx22, n2–1, sx12, sx22, df :, – o )+ t, – o2)– tdf, Upper = (o, Upper = (o1, Lower = (o1

7-10-9

Confidence Intervals

When the two population standard deviations are equal (pooled)

			α
Lower = (o1	– o2)– tn1+n2	–2		sp2		1		+		1
			2						n2
						n1
			α
Upper = (o1	– o2)+ tn1+n2	–2		sp2	1		+		1
			2						n2
					n1

When the two population standard deviations are not equal (not pooled)

Lower = (o1	– o2)– tdf	α	sx12	+		sx22
		2	n1			n2
Upper = (o	– o )+ t	α	sx12		+	sx22
		2	n1			n2
1	2 df

df =		1
	C2	+		(1–C)2
	n1–1			n2–1
		sx12
C =			n1
	sx12		+	sx22
	n1			n2

Definition of Terms

C-Level :	confidence level (0 < C-Level < 1)
List(1) :	list where sample 1 data is located
List(2) :	list where sample 2 data is located
Freq(1) :	frequency of sample 1 (1 or list name)
Freq(2) :	frequency of sample 2 (1 or list name)
Pooled :	On or Off
o1 :	sample mean of sample 1 data
sx1:	sample standard deviation of sample 1 (sx1 > 0)
n1 :	size of sample 1 (positive integer)
o2 :	sample mean of sample 2 data
sx2 :	sample standard deviation of sample 2 (sx2 > 0)
n2 :	size of sample 2 (positive integer)
Calculation Result Output
Lower :	interval lower limit (left edge)
Upper :	interval upper limit (right edge)
df :	degrees of freedom
o1 :	sample mean of sample 1 data
o2 :	sample mean of sample 2 data
sx1 :	sample standard deviation of sample 1
sx2 :	sample standard deviation of sample 2
sp :	pooled sample standard deviation (Displayed only when pooling is
	turned on.)
n1 :	size of sample 1
n2 :	size of sample 2

20090601