Hi Damien,
In my opinion this is by design. If Standard deviation is zero, then the Latest Baseline Threshold can not be calculated. This happens if all data have the same (constant) value during time.
from below formulas you can see if ${STD_DEV} (standard deviation) is zero, then the levels of thresholds can not be calculated and all values are the same.
Statistical Baseline formulas (for operator greater than):
warning threshold: ${MEAN} + 2 * ${STD_DEV}
critical threshold: ${MEAN} + 3 * ${STD_DEV}
Statistical Baseline formulas (for operator less than):
warning threshold: ${MEAN} - 2 * ${STD_DEV}
critical threshold: ${MEAN} - 3 * ${STD_DEV}
in this case you will get messages:
Statistics are not available. Standard deviation is zero.
Both the warning and critical thresholds have the same value.
when Standard deviation is zero? This happens if polled values are the same for all the time (for example Percent Packet Loss can be constantly 0%).
Workaround: In case the polled value is not changing during time much and there is a big change of getting Standard deviation zero, please do not use the "Dynamic Baseline Thresholds" calculation, but rather use the manual input of values of your choice (just manualy type values into threshold input fields for warning and critical level).
BR
Libor