Scientists must be impartial and not base their conclusions on
a.
opinions
c.
models
b.
evidence
d.
experiments

Scientists are supposed to base their conclusions on
observations ... things they can see and measure.

They make models, out of toothpicks or software, and
see how the models behave.

They examine things happening in nature, and look for
evidence in the things they see happening.

The construct experiments, and watch what happens as
the experiment proceeds, under the command of nature.

Opinion, even from many people, is not a good way to
make progress in a scientific investigation.

This is also the reason why it's not a good idea to learn
your science from a lot of people who have maybe read
about something in a newspaper, or on the internet. 
None of those people actually learned anything from
newspapers or the internet, because the stuff in the
newspapers is watered down to suit the 'average' reader
and to sell newspapers, and the click-bait on the internet
is written to sell the ads on the pages you click through to.
What you get from all the people who took their information
in those places is a bunch of opinions, and impressions of
which half came from misunderstanding what they read, all
signifying nothing and of no value to you.

Scientists must be impartial and not base their conclusions on opinions

Efficiency is an act of doing something