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Core Mathematics - Practice question

Practice question

Absenteeism v. exam scores

A teacher is conducting a study to examine the relationship between
students' absences and their examination scores. Some of the data are shown
below:

DAYS ABSENT (X)
EXAM SCORE (Y)

1
95

50
60

20
78

60
50

25
70

100
20

10
80

40
64

110
10

15
87

(a) Determine the dependent and independent variable.

(b) Construct a scatterplot of the data.

(c) Use your calculator to calculate the correlation coefficient between
days absent and exam score. Interpret your findings.

(d) Calculate the coefficient of determination and

(e) Comment on the meaning of this figure.

(a) dependent variable - exam score independent variable - days absent

(b) see graph opposite

(c) r = -0.99 A strong negative relationship, i.e. as number of days
absent increases, exam score tends to decrease.

(d) r = 0.9848 (98.48%)

(e) This means that 98.48% of the variation in one variable can be
explained by its relationship to the other.

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