cfme.utils.stats module

cfme.utils.stats.tol_check(ref, compare, min_error=0.05, low_val_correction=3.0)[source]

Tolerance check

The tolerance check is very simple. In essence it checks to ensure that the compare value is within min_error percentage of the ref value. However there are special conditions.

If the ref value is zero == the compare value we will alwys return True to avoid calculation overhead.

If the ref value is zero we check if the compare value is below the low_val_correction threshold.

The low value correction is also used if ref is small. In this case, if one minus the difference of the ref and low value correction / reference value yields greater error correction, then this is used.

For example, if the reference was 1 and the compare was 2, with a min_error set to the default, the tolerance check would return False. At low values this is probably undesirable and so, the low_val_correction allows for a greater amount of error at low values. As an example, with the lvc set to 3, the allowe error would be much higher, allowing the tolerance check to pass.

The lvc will only take effect if the error it produces is greater than the min_error.

  • ref – The reference value

  • compare – The comparison value

  • min_error – The minimum allowed error

  • low_val_correction – A correction value for lower values