Bias is tricky to measure. To measure it you have to get someone to take an IAT test. You can do it here: https://implicit.harvard.edu/implicit/takeatest.html IAT stands for Implicit Association Test.
It would be interesting if Harvard came up with an IAT test for Pro or Anti Scottish Independence!
What it does is test your responses to certain questions. It would be interesting to get Nick Robinson to do a test about Scottish Independence and his allegiance. With the thousands of people protesting about his bias - that might clear up a few things.
Bias is often subtle. There are things called micro - inequities which are small subtleties in the way we behave and communicate.
In Wikipedia it talks of Mary Rowe's original article where she defines micro-inequities
as “apparently small events which are often ephemeral and hard-to-prove, events which are covert, often unintentional, frequently unrecognized by the perpetrator".
They can be small things like forgetting who said what after a meeting to support your bias. Thinking a friend said something you support , when in fact it was someone else. It can also be small things like who you look at. Or taking preference to your own belief being supported and using more of that language than the opposing view.
in journalism it can be subtle things like where you position a picture in your report. A picture that starts a reporters piece is very telling. Most people remember the first or last thing they see for longer than other parts of a story. So what you start or finish with will be remembered for longer.
Slight word changes like using "when" rather than "if" or in the case of business leaders discussing prices; "increase" is used when "different" was said.
The tones of voice can also have micro-inequities. These subtleties are registered by our subconscious. So although the words may be technically not biased, the tone in which it is delivered could be.
So how is bias measured? In order to be deemed impartial, what is the scientific measurement that it goes through? Or is it simply someone else's opinion?