What STDEV.P does
STDEV.P measures how spread out values are around their mean when you have the entire population you want to describe. For example, use it for every order packed on Monday if your report is specifically about Monday's orders.
The result uses the same units as your data. STDEV.P divides the sum of squared differences from the mean by n, the number of numeric observations, then takes the square root.
Practical examples
Describe all orders from one day
Suppose Monday had exactly four orders, with these packing times in A2:A5:
| Cell | Minutes |
|---|---|
| A2 | 2 |
| A3 | 4 |
| A4 | 6 |
| A5 | 8 |
In C2, enter:
=STDEV.P(A2:A5)The result is approximately 2.236067977 minutes. The mean is 5, and the squared differences total 20. Divide 20 by the four observations, then take the square root of 5.
Compare another complete day's orders
Suppose Tuesday also had exactly four orders. Enter their packing times of 1, 2, 3, and 4 minutes in B2:B5 respectively. In D2, enter:
=STDEV.P(B2:B5)The result is approximately 1.118033989 minutes. The mean is 2.5, and the squared differences total 5. The square root of 5 ÷ 4 gives Tuesday's population standard deviation. Tuesday's packing times are less spread out than Monday's.
Common mistakes and notes
A complete export may still be a sample
If you're using Monday's orders to estimate variation across all orders, use STDEV.S. The choice depends on the group your report describes. See standard deviation in Excel for both calculations on the same values.
Count observations, including zero
STDEV.P ignores empty cells, text, numbers stored as text, and logical values in a referenced range. Zero is included. Check the numeric cell count with COUNT, especially after importing data.
With one numeric observation, the population standard deviation is 0: that value has no distance from its own mean. With no numeric observations, the calculation returns #DIV/0!.
Direct arguments can change what gets counted
In =STDEV.P(2,4,"8"), the quoted 8 counts as a number. In =STDEV.P(2,4,TRUE), TRUE counts as 1. Text that cannot be converted to a number causes an error. If you need to count text and logical values from references, check STDEVPA's rules before changing functions.
Investigate errors in the source range
A documented Excel for Mac check returned #N/A when a referenced range contained =NA(). Don't rely on STDEV.P to skip error cells. Fix the source error before interpreting the result; replacing it with zero changes the data.
The Microsoft reference currently says errors in arrays or references are ignored. That wording conflicts with the observed Excel result, so the error-propagation note here is based on the Excel check.