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2.5.6 Pearson's product-moment correlation coefficient

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Question 65

A biochemist monitors the relationship between the concentration of a specific catalyst, ccc mmol/L, and the resulting reaction rate, rrr μ\muμmol/s, for 10 distinct chemical trials. The experimental results are summarized as follows:

∑c2=9625∑cr=6792.5∑c=275∑r=220Srr=325 \sum c^2 = 9625 \quad \sum cr = 6792.5 \quad \sum c = 275 \quad \sum r = 220 \quad S_{rr} = 325 ∑c2=9625∑cr=6792.5∑c=275∑r=220Srr​=325
a.

Determine the values of SccS_{cc}Scc​ and ScrS_{cr}Scr​ for this experiment.

[2]
b.

Calculate, to 3 significant figures, the product moment correlation coefficient (PMCC) between ccc and rrr.

[2]
c.

Find the equation of the least squares regression line of rrr on ccc in the form r=a+bcr = a + bcr=a+bc.

[3]
d.

Identify which of the two variables is the explanatory variable in this study, providing a reason for your choice.

[1]
e.

Using your regression model, estimate: (i) the reaction rate when the concentration of the catalyst is 32 mmol/L, (ii) the total change in the reaction rate for an 8 mmol/L increase in concentration.

[3]
f.

It was later found that one trial, where the concentration was 20 mmol/L and the reaction rate was 45 μ\muμmol/s, was incorrectly transcribed and is considered an outlier.

State, with a reason, the effect that removing this outlier would have on the value of the PMCC.

[2]

2.5.6 Pearson's product-moment correlation coefficient Questions

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