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2.2.2 Scatter diagrams and correlation

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Question 60

A marine biologist is investigating the relationship between the concentration of a specific mineral, mmm in parts per million (ppm), and the annual growth rate of a particular coral species, GGG in mm per year, across 8 distinct reef locations. The observations are recorded in the table below.

Reef Site12345678
Mineral Concentration mmm (ppm)6.012.017.021.026.030.034.038.0
Growth Rate GGG (mm/year)4.56.78.910.112.514.115.917.3

You may use the following summary statistics: Smm=854.0S_{mm} = 854.0Smm​=854.0 SmG=346.8S_{mG} = 346.8SmG​=346.8 SGG=141.0S_{GG} = 141.0SGG​=141.0 ∑m=184.0\sum m = 184.0∑m=184.0 ∑G=90.0\sum G = 90.0∑G=90.0

a.

Find the product moment correlation coefficient between GGG and mmm.

[2]
b.

Give a reason why a linear regression model of the form G=a+bmG = a + bmG=a+bm is appropriate for these data.

[1]
c.

Find the value of bbb correct to 3 decimal places.

[2]
d.

Find the equation of the regression line of GGG on mmm.

[3]
e.

Interpret your value of bbb in context.

[1]
f.

Use your answer to part (d) to estimate the growth rate of the coral when the mineral concentration is 25.025.025.0 ppm.

[2]
g.

Comment on the reliability of your estimate in part (f), giving a reason.

[1]

2.2.2 Scatter diagrams and correlation Questions

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