Uni-edit English Writing Tip 011

How to significantly improve your usage of the term ‘significant’

Difficulty: Intermediate

How many times have you seen the word ‘significant’ used in a scientific
paper either with statistical results or to discuss the importance of
something? Did you know its meaning is different depending on if it is
used in a statistical or non-statistical sense?

For example, what’s wrong with this sentence from a paper’s Discussion
section?

Significant levels of bisphenol-A were detected in 47 of the 50 sites
sampled (85.0%).

What is clear is that ‘significant’ is used in a general sense, to
indicate degree or extent. What is unclear is whether the author is
referring to the levels’ importance or relevance, or instead to a
statistical, quantitative interpretation. To make this writing tip easy
to follow and distinguish common examples, we divide ‘significant’ into
two categories: ‘statistical’ and ‘non-statistical’.

Statistical Usage In its statistical sense, ‘significant’ is commonly
used in the Results section to indicate how much a variable differs from
a null hypothesis or baseline measurement based on the P-value, usually
P\<0.05.

There was a statistically significant difference between the experiment
and control groups (P\<0.05), leading us to reject our null hypothesis.

This means the quantitative difference between the two groups was large
enough to satisfy the statistical criteria of the analysis comparing the
two groups.

By the way, it is often more effective and natural to combine the adverb
form ‘significantly’ with an adjective, so that readers intuitively
understand the axis of measurement.

Okay: There was a statistically significant difference between the time
taken by our nutrient extraction method to extract 1 kg of oleic acid
and that taken by the leading conventional method (Robinson et al.,
2015) (6.3±1.2 h vs. 8.0±0.5 h; p=0.032).

Non-statistical Usage In its non-statistical sense, ‘significant’ is
commonly used to express the importance or relevance of something,
generally speaking.

Iron ore is a significant export contributing to Australia’s economy.
This could be rephrased to: Iron is an important export contributing to
Australia’s economy.

Our finding that rice paddy runoff reduces salinity of adjacent lagoons
bears significance on India’s aquacultural policy. This could be
rephrased to: Our finding that rice paddy runoff reduces the salinity of
adjacent lagoons has relevance to India’s aquacultural policy.

The meanings here are general. For example, the first sentence does not
mean that all of Australia’s exports were analyzed, and our statistical
results give us confidence that the quantity of iron was greater than
another export. It just means Australia exports a lot of iron (it also
exports a lot of wheat and wool, but that’s not relevant here).

Resolving ambiguity - Example 1 Significant levels of bisphenol-A were
detected in 47 of the 50 sites sampled (85.0%).

Does the author mean that the levels were significantly higher with
respect to a standard or baseline measurement? Or that these results
were important (and thus cause for concern)? This sentence requires
major revision, even if both usages were intended: 1.) Based on the
grammar alone, a reader is justified in assuming bisphenol-A is good,
and that low levels are cause for concern. 2.) There is no object of
comparison: what are the levels higher (or lower) than?

Important: The high levels of bisphenol-A detected in 47 of the 50 sites
samples (85.0%) are cause for concern. Statistically significant: Levels
of bisphenol-A significantly higher (p\<0.001) than the amount EPA
guidelines consider safe were detected in 47 of the 50 sites sampled
(85.0%).

Resolving ambiguity - Example 2 Our results agree with the significant
findings of Kang et al. (2006), who found that β-carotene production was
more efficient in 5% kerosene-supplemented media than in
non-supplemented media.

The author likely means both! If Kang et al.’s findings were both
statistically significant and ground-breaking, this usage is acceptable.
However, we can limit the word to one of these usages if warranted
(e.g., if Kang et al.’s findings were not particularly novel).

Important: Our results agree with the major findings of Kang et al.
(2006), who found that β-carotene production was more efficient in 5%
kerosene-supplemented media than in non-supplemented media.
Statistically significant: Our results agree with the findings of Kang
et al. (2006), who found that β-carotene production was significantly
more efficient in 5% kerosene-supplemented media than in
non-supplemented media (F4,15 = 25.6, P \< 0.001).

Conclusion The take-home messages from the above examples are: 1.)
Significance is used to measure quantity, importance, and relevance; and
2.) Its usages can be conveniently categorized as ‘statistical’ and
‘non-statistical’.

END OF TIP