Statistics has its own jargon. Always keep your audience in mind. Will they be comfortable with terms such as significance testing, multivariate analysis and confidence interval? If not, can you define the terms or rearrange the discussion to do without them? Conversely, avoid talking down to experts.
Here are a few examples of choosing the right terminology.
Average vs mean
The average is obtained by adding up the values and dividing by how many there are. Within statistics, it is known as the (arithmetic) mean. But, unless your audience is mathematically literate, use average.
Percentages, rates and proportions
In 2017, more than a quarter of deaths in Australia were caused by cardiovascular disease. This can be expressed in several ways:
| Percentage |
27% |
|
Proportion
|
0.27 or ‘more than a quarter’
|
|
Rate
|
1 in 4
|
Source: Cardiovascular disease
In a technical publication, use the percentage (or the proportion in decimal terms). It is precise. Use the rate (or the proportion in verbal terms, such as more than a quarter) when writing for a broad audience. This is more human and immediate, although it lacks the precision to please an expert.
Take care when discussing changes in percentages:
If 5% of the population was vegetarian in 2010 and 10% of the population was vegetarian in 2020, this does not mean:
Vegetarianism has grown by 5% over the decade. [This would be an increase of 5% of 5%, or 5.25% in 2020]
It should be expressed as:
Vegetarianism has grown by 5 percentage points to 10%.
or:
Vegetarianism has grown from 5% of the population in 2010 to 10% in 2020.
Probabilities
Impossible events have a probability of 0, certain events a probability of 1. The probability of tossing a head (or tail) with a fair coin is 0.5.
Consider reminding your audience that probabilities cannot predict the outcome of a single event. Probabilities do not say what will happen, only what will happen on average.
Do not confuse probabilities with odds:
- Probability of rolling a 2 on a fair dice: 1 ÷ 6 = 1.67 (1 of 6 possible outcomes).
- Odds of rolling a 2 on a fair dice: 1:5 (1 outcome is a 2; 5 outcomes are not a 2).
Avoid discussions in terms of odds unless you are sure your audience is familiar with the idea.
Taking care with technical terms
Some words have specific meanings within data and statistics. Use them with care. When in doubt, check. Here are a few examples.
|
Word
|
Does mean
|
Does not mean
|
|
Significant
|
The result has been shown by rigorous statistical tests to be likely to be real (with a specified probability)
|
- Big
- Impressive
- Wow! I did not expect that
|
|
Trend
|
A consistent pattern that occurs over a fairly long period
|
- Something that happens once (or even twice)
- Something that is common
- A fashion (something ‘trendy’)
- A change in behaviour (such as a change in slope of a graph)
|
|
Average
|
I have added up all the values and divided by the number of values
|
- Typical
- Normal
- Usual
- Disappointing (‘that was pretty average’)
|
|
Normal
|
Distributed according to the ‘normal’ distribution (the technical term synonymous with the bell curve)
|
- Typical
- Usual
- As expected
|
Always look out for terms that could be confusing, ambiguous or misunderstood. Use the word that has the fewest possible interpretations.
