October 2020 Paper 2 Q11

OCR MEICurrent spec10 marksCorrelation & RegressionLarge Data Set

11 The pre-release material contains information concerning median house prices over the period 2004 – 2015. A spreadsheet has been used to generate a time series graph for two areas: the London borough of “Barking and Dagenham” and “North West”. This is shown together with the raw data in Fig. 11.1.

Fig. 11.1: time series graph of median house price from 2004 to 2015; Barking and Dagenham (dashed) is always above North West (solid)
YearBarking and DagenhamNorth West
2004160 000107 000
2005163 000118 000
2006168 000127 000
2007185 000134 750
2008190 000129 950
2009160 000130 000
2010171 000130 000
2011170 000127 000
2012174 995130 000
2013180 995131 000
2014215 000138 500
2015243 500140 000

Fig. 11.1

Dr Procter suggests that it is unusual for median house prices in a London borough to be consistently higher than those in other parts of the country.

(a) Use your knowledge of the large data set to comment on Dr Procter’s suggestion. [1]

Dr Procter wishes to predict the median house price in Barking and Dagenham in 2016. She uses the spreadsheet function LINEST to find the equation of the line of best fit for the given data. She obtains the equation

\(P = 4897Y - 9\,657\,847\), where \(P\) is the median house price in pounds and \(Y\) is the calendar year, for example 2015.

(b) Use Dr Procter’s equation to predict the median house price in Barking and Dagenham in
  • 2016
  • 2017.
[2]

Professor Jackson uses a simpler model by using the data from 2014 and 2015 only to form a straight-line model.

(c) Find the equation Professor Jackson uses in her model. [2]
(d) Use Professor Jackson’s equation to predict the median house price in Barking and Dagenham in
  • 2016
  • 2017.
[2]

Professor Jackson carries out some research online. She finds some information about median house prices in Barking and Dagenham, which is shown in Fig. 11.2.

20162017
£290 000£300 000
Fig. 11.2

(e) Comment on how well
  • Dr Procter’s model fits the data,
  • Professor Jackson’s model fits the data.
[2]
(f) Explain which, if any, of the models is likely to be more reliable for predicting median house prices in Barking and Dagenham in 2020. [1]
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