5.3.4. Statistical analysis
1) The validity of a test depends on some data validity range.
2) In negative reference samples, larval mortality (number of dead larvae/48), pupal mortality (number of dead pupae at D22/number of alive pre pupae at D7) and adult mortality (number of dead emerged bees at D22/total number of emerged bees) must be lower or equal to 15% for the assessment of LD50 or LC50, or 20% for the assessment of NOAEL or NOAEC. In case of higher mortality in the control sample, the replicate is invalidated.
3) The mortality rate with positive reference (dimethoate) must be:
- higher than or equal to 50% at D6 for larvae
exposed to 3µg/larva at D4
- higher than or equal to 50% at D7 in chronic exposure of larvae to the concentration 20,000µg/kg diet.
4) The calculated LD50 and LC50 must in each case be between the two extreme tested doses. They must not be extrapolated out of the tested limits.
5) Any deviation from the above conditions will invalidate the test.
6) LD50 and LC50 are calculated from mortalities expressed in percentage of the reference populations after an adjustment according to the Abbott or Shneider-Orelli formula (see section 8.4.1.).
6) The results will be analysed using regression model with high adjustment level, which can be checked with the determination coefficient value (Abbott, 1925).
7) Basing on the same raw mortality data, the NOAEL and NOAEC are assessed (see section 8.4.3.).