WJEC Further Unit 2 2019 June — Question 7

Exam BoardWJEC
ModuleFurther Unit 2 (Further Unit 2)
Year2019
SessionJune
TopicLinear regression
TypeHypothesis test for zero correlation

7. An article published in a medical journal investigated sports injuries in adolescents' ball games: football, handball and basketball. In a study of 906 randomly selected adolescent players in the three ball games, 379 players incurred injuries over the course of one year of playing the sport. Rhian wants to test whether there is an association between the site of injury and the sport played. A summary of the injuries is shown in the table below.
\multirow{2}{*}{}Site of injury
Observed valuesShoulder/ ArmHand/ FingersThigh/ LegKneeAnkleFootOtherTotal
\multirow{3}{*}{Sport}Football834536513612191
Handball14266154266115
Basketball428442211073
Total265755551154328379
  1. Calculate the values of \(A , B , C\) in the tables below.
    \multirow{2}{*}{}Site of injury
    Expected valuesShoulder/ ArmHand/ FingersThigh/ LegKneeAnkleFootOther
    \multirow{3}{*}{sodod}Football13.102928.725627.717727.717757.955121.670214.1108
    Handball7.889217.295516.688716.6887A13.04758.4960
    Basketball5.007910.978910.593710.593722.15048.28235.3931
    \multirow{2}{*}{}\multirow[b]{2}{*}{Chi-Squared Contributions}Site of injury
    Shoulder/ ArmHand/ FingersThigh/ LegKneeAnkleFootOther
    \multirow{3}{*}{sodoct}Football1.9873223.03890\(10 \cdot 77575\)2.47484\(B\)9.475860.31575
    Handball4.733334.38079C0.170871.446903.806640.73331
    Basketball0.2028626.388654.104004.104000.001026.403063.93521
  2. Given that the test statistic, \(X ^ { 2 }\), is 116.16, carry out the significance test at the \(5 \%\) level.
  3. Which site of injury most affects the conclusion of this test? Comment on your answer. Rhian also analyses the data on the type of contact that caused the injuries and the sport in which they occur, shown in the table below.
    Observed valuesBallOpponentSurfaceNoneTotal
    Football17681792194
    Handball23341938114
    Basketball2817121471
    Total6811948144379
    The chi-squared test statistic is 46.0937 . Rhian notes that this value is smaller than 116.16 , the test statistic in part (b). She concludes that there is weaker evidence for association in this case than there was in part (b).
  4. State Rhian's misconception and explain what she should consider instead. \section*{END OF PAPER}