A female acquaintance of mine was recently surprised to find that both of her sons were colourblind, despite neither parent being colourblind. A natural question to ask is ‘What are the odds?’ This question turns out to be open to interpretation, depending on what we mean by probability and odds.

# Month: June 2018

## Primary, secondary and ternary sources

I am a bit annoyed that scientists don’t always seem to get the difference between primary, secondary and tertiary sources. Consider this situation:

- Prince (2008) reports that pigs are approximately blue.
- Quail (2006), Quaffer (2008) and Qi (2009) use the approximation that pigs are blue.
- Rout (2012) is a review article discussing the aforementioned works.

Which of the following are valid?

- ‘Pigs are approximately blue (Prince 2008).’
- ‘Pigs are approximately blue (Quail 2006, Quaffer 2008, Qi 2009).’
- ‘We use the approximation that pigs are blue (Prince 2008).’
- ‘We use the approximation that pigs are blue (Quail 2006, Quaffer 2008, Qi 2009).’
- ‘We use the widely-used approximation that pigs are blue (Quail 2006, Quaffer 2008, Qi 2009).’
- ‘We use the widely-used approximation that pigs are blue (Rout 2012).’
- ‘The approximation that pigs are blue is widely used (Quail 2006, Quaffer 2008, Qi 2009).’
- ‘The approximation that pigs are blue is widely used (Rout 2012).’
- ‘Many authors, including Quail (2006), Quaffer (2008) and Qi (2009), use the approximation that pigs are blue.’
- ‘Many authors, including Quail (2006), Quaffer (2008) and Qi (2009), use the approximation that pigs are blue (Rout 2012).’