University of the West of England

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Chi-Squared Contingency Table (car colour and speed)

 

Link to Video Answer

 

A student investigates whether there is a relationship between the colour of the car and the speed at which it is driven. Selecting an open stretch of road, he counts the numbers of cars of each colour that could be considered to be driving Very Fast, Fast, At a Moderate Speed, or Slowly. The Observed Frequencies are given in the table:

 

 

Red

Green

Very Fast

5

1

Fast

20

24

Moderate

12

18

Slow

3

17

 

Use Minitab to

 

i)          perform a chi-squared contingency test, using the above categories of speed, to investigate whether there is a relationship between the colour of the car and the speed at which it is being driven,

 

ii)         explain why it is necessary to modify the data in order to perform a reliable chi-squared test,

 

iii)        perform the modified test.