OCR S1 2012 June — Question 1

Exam BoardOCR
ModuleS1 (Statistics 1)
Year2012
SessionJune
TopicLinear regression
TypeInterpret correlation strength/direction

1 For each of the last five years the number of tourists, \(x\) thousands, visiting Sackton, and the average weekly sales, \(\pounds y\) thousands, in Sackton Stores were noted. The table shows the results.
Year20072008200920102011
\(x\)250270264290292
\(y\)4.23.73.23.53.0
  1. Calculate the product moment correlation coefficient \(r\) between \(x\) and \(y\).
  2. It is required to estimate the average weekly sales at Sackton Stores in a year when the number of tourists is 280000 . Calculate the equation of an appropriate regression line, and use it to find this estimate.
  3. Over a longer period the value of \(r\) is - 0.8 . The mayor says, "This shows that having more tourists causes sales at Sackton Stores to decrease." Give a reason why this statement is not correct.