HP 39gs Master Guide

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Grade awarded
A teacher wishes to decide, at the 5% level of significance,
Year A B Total
whether the performance in a problem solving test is
8 22 18 40
independent of the students’ year at school. The teacher
9 26 14 40
selected 120 students, 40 from each of Years 8, 9 & 10, and
10 27 13 40
graded their performance in a test as either A or B.
Total 75 45 120
The table above right shows the results of his testing.
The hypotheses being tested are:
H
0
: There is no relationship between grades awarded
and years at school. They are independent.
H
A
: There is a relationship.
Year
Grade awarded
A B
Total
8 25 15 40
If H
0
is true then the expected frequencies should be those in the table
on the right.
9
10
Total
25
25
75
15
15
45
40
40
120
Enter the observed and expected frequencies into columns
C1 and C2 of
the Statistics aplet.
In the
HOME view, perform the calculation shown right. This calculates
the individual
χ
2
values ready for summing as per the formula
−
2
χ
=
∑
(
OE
)
, where O and E are the observed and expected
E
frequencies.
After first changing to the
SYMB view to register C3, the required total
for
C3 can be found in the view. In this case, 1.493.
312

HP 39gs Specifications

General

Type	Scientific
Form factor	Pocket
Product color	Gray
Internal memory	0.256 MB

Weight and Dimensions

Weight	249 g
Dimensions (WxDxH)	187 x 94 x 31 mm