> Design to be inclusive, and everyone benefits.<p>Note that this is not always true. For example the tax instructions in the US are designed to be able to be followed by anyone (add line 3 to line 4. Subtract line 1 from line 5. Multiply line 6 by 2. etc.), but the result is that things like piecewise linear functions that anyone comfortable with basic arithmetic and algebra would understand at a glance become a completely incomprehensible 25 step worksheet that's basically an assembly program for humans to follow.<p>So keep in mind that things like algebra and equations don't just exist to torture people. They actually make it easier to understand and explain a lot of concepts.
> Do round numbers to the nearest whole number [and do not use decimals unless it's money]<p>is very bad advice and may lead to all kinds of inappropriate rounding. Trying to find an additional representation (possibly visually) without using decimals or percentage would be much better guidance.
This is an interesting read, but I note that when you get a car tax reminder in the UK, there is a 12 digit document reference number, presented as three groups of 4 digits, and last time I used it, you couldn't enter the number with the spaces. Trivial for a programmer to fix, but really annoying for users.
Numbers are tough for everyone.<p>Most people are incapable of correctly estimating so this should never be left as an exercise to the reader. This also includes using precise numbers where the precision does not matter. For what it is worth, for me pi=3 and pi^2=10.<p>This is particularly visible when statistical data come to play. It is very easy to misinterpret these numbers, so they should be put in context. Unfortunately this means that they suddenly so to be ready to convey.
relevant blog post from a friend of mine <a href="https://gigi.montaigne.io/why-do-i-like-feynman" rel="nofollow">https://gigi.montaigne.io/why-do-i-like-feynman</a>
I think the design advice given applies for ALL users, even those who are fluent with numbers. Any one of us, barring Spock from the planet Vulcan can become overwhelmed with numbers. if there’s a way to accomplish the design goal without actual numbers and should be preferred.
Long codes should always be designed assuming failure is common(If I have to enter a 20 digit serial number there should always be a way to fix it).<p>Pull to refresh absolutely needs to be configurable, and I'm not sure how any company that claims to care about accessibility would force such a horrific feature on the world.
<i>...always try to round values up to a whole number, and get rid of decimal places unless it’s money</i><p>With money, I think rounding prices to the nearest 5 pence (cent) would make sums easier for everyone. Getting rid of 1 pence and 2 pence coins is overdue (in UK).