1 / 18

Anders Bignert , Dep. of Contaminant Research 06.10.27

Randomization and stratification — a model analysis at different variation scenarios. Swedish Museum of Natural History. Anders Bignert , Dep. of Contaminant Research 06.10.27. Timeseries. Tidsserier. Sampling frequency. SD(lr) = 0.35. Sampling period = 12 years.

aideen
Télécharger la présentation

Anders Bignert , Dep. of Contaminant Research 06.10.27

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Randomization and stratification — a model analysis at different variation scenarios Swedish Museum of Natural History Anders Bignert, Dep. of Contaminant Research 06.10.27

  2. Timeseries Tidsserier

  3. Sampling frequency SD(lr) = 0.35 Sampling period = 12 years Power as a function of slope (annual change in %) at log-linear regression analysis at a residual standard deviation on a log-scale of 0.35, assuming normally distributed residuals. The graphs, from left to right, represent sampling every, every-second, third and fourth year, respectively based on Monte Carlo simulations at 10,000 runs.

  4. Spatial monitoringObjectives? • Estimate mean and variance • Regional differences • Spatial trends • Level in relation to class limit

  5. Sample variogram Figur II. Variogram som visar hur skillnaden mellan prov (CB-118, pg/g färskvikt i strömmings­muskel från Bottenhavet) ökar med ökande avstånd.

  6. N of species – n of samples (nets) Randomization technique

  7. Unaligned square lattice design Random design Sobol sequence Sampling design

  8. CV = 10% Distance to class limit: 25, 15, 10 , 5%

  9. CV=20%, normal distributed Distance to class limit: 30, 25, 20, 15, 10% 10 > 34

  10. CV=20%, Log-normal distribution Distance to class limit: 30, 25, 20, 15, 10% 34 > 50

  11. random sampling Sobol sequence 75 > 53

  12. random sampling ”Stratified” sampling 100 > 65

  13. 35% (normally distributed) variation were added (> total variation = 39 %) True mean = 2.5 pg/g. Distance to4.0, 3.5 and 3.0 pg/g (37.5%, 28%, 17%)

  14. Afla-toxines in figs Tolerance limit

  15. PCDD/DF - TEQ Herring, geometric mean Muscle

  16. PCDD/DF- TEQ Herring, 95% conf. int. Muscle

  17. PCDD/DF- TEQ Herring, 95% pop int. Muscle

More Related