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2.2.2 Scatter diagrams and correlation

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Question 69

An industrial chemist is investigating the relationship between the reaction temperature, T T\,T in Kelvin (K\text{K}K), and the resulting chemical yield, Y Y\,Y in grams (g\text{g}g), of a specific synthetic process. A series of 12 experimental trials is conducted, and the data are recorded.

The summary statistics for the trials are as follows:

n=12,∑T=3900,∑Y=1800,∑Y2=273600,STT=2400,STY=2100 n = 12, \quad \sum T = 3900, \quad \sum Y = 1800, \quad \sum Y^2 = 273600, \quad S_{TT} = 2400, \quad S_{TY} = 2100 n=12,∑T=3900,∑Y=1800,∑Y2=273600,STT​=2400,STY​=2100
a.

Calculate the product moment correlation coefficient between T T\,T and YYY.

[3]
b.

Give an interpretation of your product moment correlation coefficient in the context of the study.

[1]
c.

Find the equation of the least squares regression line of Y Y\,Y on T T\,T in the form Y=a+bTY = a + bTY=a+bT.

[3]
d.

Give an interpretation of the value of b b\,b in your regression line.

[1]
e.

(i) Use the regression line from part (c) to estimate the chemical yield for a reaction performed at a temperature of 380 K.

(ii) Comment on the reliability of your answer in part (i) given that the range of temperatures in the sample was 305 K to 345 K.

[2]
f.

Using the regression line from part (c), the researcher estimates that for a temperature increase of x Kx\text{ K}x K, there will be an increase of 14 g in the chemical yield.

Find the value of xxx.

[2]

2.2.2 Scatter diagrams and correlation Questions

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  3. /2.2.2 Scatter diagrams and correlation