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2.5.6 Pearson's product-moment correlation coefficient

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Question 92

A marine biologist monitors a population of Great White Sharks, collecting data on the total length, LLL meters, and the body mass, MMM tonnes, of 12 specimen sharks. The data is summarised as follows:

SLL=19.4S_{LL} = 19.4SLL​=19.4 ∑M2=69.67\sum M^2 = 69.67∑M2=69.67 ∑LM=123.46\sum LM = 123.46∑LM=123.46 ∑L=50.4\sum L = 50.4∑L=50.4 ∑M=25.8\sum M = 25.8∑M=25.8

a.

Calculate the value of SLMS_{LM}SLM​ and the value of SMMS_{MM}SMM​.

[2]
b.

Calculate the value of the product moment correlation coefficient (PMCC) between LLL and MMM.

[2]
c.

Show that the equation of the regression line of MMM on LLL can be written as

M=−1.12+0.778L M = -1.12 + 0.778L M=−1.12+0.778L

(Rounding constants to 3 significant figures).

[3]
d.

Give an interpretation of the gradient of the regression line.

[1]
e.

Explain why it would not be appropriate to use this regression line to estimate the mass of a shark with a total length of 1.2 meters.

[1]
f.

The biologist decides to code the data using u=L−2u = L - 2u=L−2 and v=5M+3v = 5M + 3v=5M+3.

Write down the value of the PMCC between uuu and vvv.

[1]
g.

Write down an equation of the regression line of vvv on uuu. You do not need to simplify your equation.

[1]

2.5.6 Pearson's product-moment correlation coefficient Questions

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  3. /2.5.6 Pearson's product-moment correlation coefficient