- Is the input data good?
*Garbage in, garbage out!*- Is the data source authoritative? (
*Don't trust it!*) - Was the data measured accurately?
- How much noise does the data have?
- Was the data recorded accurately?
- Does the data mean what it is alleged to mean?

- Is the data source authoritative? (
- Is the algorithm correct?
- Is the algorithm an accurate model of reality?
- Are the answers numerically accurate?
- Is the data represented accurately?
- 32-bit
`int`: 9 decimal digits - 64-bit
`long`: 19 decimal digits - 32-bit
`float`: 7 decimal digits (*avoid!*)

Patriot missile: inaccurate float conversion caused range gate error: 28 killed, 98 injured. - 64-bit
`double`: 15+ decimal digits - Ariane 5: 64-bit
`double`converted to 16-bit int: overflowed, rocket exploded, $500 million loss.

- 32-bit