When the margin of error is taken into account, Labour could actually be behind the Conservatives.

BBC: Has Labour's poll slide halted?

Cities close together in the standings may have very different prices, while others further apart can be effectively level with each other, taking into account margins of error for price and expenditure data, which the firms don't share with the public.

WSJ: Useful Cost-of-Living Data Don't Come Cheap

Later that month a representative indicated that the capital gains distribution credited to her account was a computer error.

FORBES: Sodexo's Twisted 401(k)

Having established the reality of his point, he then designed a mathematical model that tried to take into account and quantify sources of error.

ECONOMIST: Just how reliable are scientific papers?

Also, take into account the possibility of human error.

BBC: NEWS | Business | Ask the expert: Switching Isas

In June, a programming error temporarily allowed any password to be used to access any account.

WSJ: Hype Hangs Over Dropbox

Keeping a cushion in your account will cover you in emergency situations and absorb the occasional accounting error.

FORBES: Become Allergic To Bank Fees

Any real-time account of what happened that night is likely to be fraught with mis-remembering and error.

FORBES: Why The Story Of Osama Bin Laden's Death Will Shift

For example, if you were visiting Mashable and logged into our site using your Facebook account (and you were also signed into Facebook), you were automatically redirected to a Facebook error page.

CNN: How Facebook (briefly) killed the Internet

In June, a programming error at Internet-based storage firm Dropbox Inc. temporarily allowed any password to be used to access any user account on its website, though Dropbox says fewer than 100 accounts were affected.

WSJ: What's a Company's Biggest Security Risk? You.