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An introduction to everyday statistics—1
  1. P Driscoll,
  2. F Lecky,
  3. M Crosby
  1. Accident and Emergency Department, Hope Hospital, Salford M6 8HD
  1. Correspondence to: Mr Driscoll, Consultant in Accident and Emergency (e-mail: pdriscoll{at}

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  • Define statistics

  • Discuss the types of data commonly encountered in accident and emergency (A&E) work

  • Describe the techniques used to summarise a single dataset

In covering these objectives we will deal with the following terms:

  • Variable

  • Discrete and continuous

  • Frequency distribution

  • Grouping

  • Transformation

Statistics is defined as a process by which numerical data are transformed into a usable form for scientific interpretation. This entails manipulating data to summarise the findings (descriptive statistics). It can also be used to develop general conclusions from the data (inferential statistics) (fig 1).

Figure 1

Relation between descriptive and inferential statistics.

It is useful to start this series by dealing with descriptive statistics because:

  • You deal with them everyday in the A&E department.

  • It will introduce the importance of knowing what type of data you are handling

  • The majority of statistical analysis starts by summarising data

To demonstrate this consider the following problem:

Dr Canute is a consultant in A&E medicine at Deathstar General. A recent visit by the audit commission has found the waiting times for paediatrics are too long and need to be cut. Galvanised into action, he asks his new specialist registrar Egbert Everard to investigate. Happy to help out, Egbert lists a number of factors he considers important. These are known as variables because they are measurements that vary between individuals.1 He asks for a print out of these variables on all paediatricarrivals in the A&E department over the past 24 hours. A button is pressed and several yards of computer printout are produced (table 1).

View this table:
Table 1

Paediatric A&E admissions in one day at Deathstar General

Key point A variable is something whose value or quality can vary

Obviously there is a lot of information here but in its current form it is not very usable. To make this more manageable, and useful, …

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  • Funding: none.

  • Conflicts of interest: none.