'Reasoning from Evidence' 
Ordering a Cab - Example #3

Malcolm Swan
Mathematics Education
University of Nottingham
Malcolm.Swan@nottingham.ac.uk

Jim Ridgway
School of Education
University of Durham
Jim.Ridgway@durham.ac.uk

The aim of this assessment are to provide the opportunity for you to:
•	use appropriate calculations to analyze data
•	use appropriate graphs and/or diagrams to analyze data
•	reason clearly and convincingly.

Sunshine cabs and Bluebird cabs are rival companies. 

Each claims that their cab company is better than the other.

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Sarah has to take a cab to work each day.  She wants to compare the two companies. 

Over several months Sarah orders each cab 20 times.  She records how early or late they are when arriving to pick her up from her home.

Her results are shown on the next page...

Cab data sheet

1.	At the moment, it is hard to see which company is the best.
	Use appropriate calculations, graphs and/or diagrams to analyze the data so that 
	comparisons are easier to make.  Show all your reasoning.
	
2.	Present a reasoned case for Sunshine cabs being the better company.
	Present your reasoning as fully and as clearly as possible.
	
3.	Present a reasoned case for Bluebird cabs being the better company.
	
4.	Which argument do you think is the most convincing? Why?