Inference Testing Using The Chi 2 Test - HP 39gs Master Manual

I n f e r e n c e t e s t i n
I n f e r e n c e t e s t i n
A teacher wishes to decide, at the 5% level of significance,
whether the performance in a problem solving test is
independent of the students' year at school. The teacher
selected 120 students, 40 from each of Years 8, 9 & 10, and
graded their performance in a test as either A or B.
The table above right shows the results of his testing.
The hypotheses being tested are:
H : There is no relationship between grades awarded
0
and years at school. They are independent.
H : There is a relationship.
A
If H is true then the expected frequencies should be those in the table
0
on the right.
Enter the observed and expected frequencies into columns
the Statistics aplet.
In the view, perform the calculation shown right. This calculates
HOME
χ
the individual values ready for summing as per the formula
2
( )
−
2
O E
∑
χ , where O and E are the observed and expected
=
2
E
frequencies.
After first changing to the
for can be found in the
C3
2
2
g u s i n g t h e C h i
g u s i n g t h e C h i
view to register
SYMB
view. In this case, 1.493.
t e s t
t e s t
and of
C1 C2
, the required total
C3
312
Grade awarded
Year A B
8 22 18
9 26 14
10 27 13
Total 75 45
Grade awarded
Year A B
8 25 15
9 25 15
10 25 15
Total 75 45
Total
40
40
40
120
Total
40
40
40
120