Missing values
Missing values can mean unknown, unavailable, or not applicable rather than zero.
Naomi opens this week's delivery report. One order shows a delay of 0, and another has an empty delay cell. Why don't the 0 and the blank tell her the same thing?
| Order | Delay (minutes) |
|---|---|
| D01 | 0 |
| D02 | |
| D03 | 8 |
4 minutes. No sign-up needed.
What you'll learn5 ideas
- A recorded zero, like a delay of 0 minutes, means someone checked and found no delay.
- A missing value means no usable value was recorded, so you can't tell what happened.
- In the delivery example, replacing the missing delay with 0 treats an unknown delay as no delay and lowers the average from 6 to 4 minutes.
- A value is unavailable when it existed but can't be obtained now, and not applicable when the field doesn't fit the case.
- A missing-value marker, like an empty cell or -999, gets its meaning only from the file's guide.