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## 'Odd One Out' printed from http://nrich.maths.org/

### Why do this problem?

This problem helps to develop the skill of working with large
sets of numbers and getting a 'feel' for their properties. Being
able to spot anomalous data quickly is very useful in industrial
and research contexts, and this problem could be considered
numerical detective work.

### Possible approach

This activity could be used with small groups of students
working on computers or with the whole class working together,
perhaps with printed copies of a dataset. Give students plenty of
time to study the data and discuss in small groups anything they
notice.

When they think they have identified an odd one out for most
or all of the six processes, students could explain to one another
how they think the processes work and how sure they are that they
have correctly identified the odd one out. They could then test
their identification of the processes with new data.

### Key questions

Are there any patterns to the data? Is there anything that
doesn't fit with the patterns you see?

Can we ever be sure that our explanation of the processes is
correct?

At what point do we accept that our explanation is
correct?

### Possible extension

There is scope for lots of statistical calculation to justify
the decisions students make for the odd ones out, by calculating
the probability of those errors arising by chance, and working out
how likely it is that the data was generated by processes other
than those they have assumed.

### Possible support

The problem

Data Matching gives an opportunity to look at and compare data
sets.