Measurement error of state variables creates substantial bias in results of demographic population models

Ecology ◽  
2018 ◽  
Vol 99 (10) ◽  
pp. 2308-2317 ◽  
Author(s):  
Allison Louthan ◽  
Daniel Doak
Keyword(s):  
Measurement Error ◽  
Population Models ◽  
State Variables ◽  
Substantial Bias

Structured Population Models

2021 ◽  
pp. 47-60
Author(s):  
Timothy E. Essington
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Matrix Model ◽  
Age Structure ◽  
Population Growth Rate ◽  
Population Models ◽  
State Variables ◽  
Elasticity Analysis ◽  
Structured Population Models ◽  
Structured Population

The chapter “Structured Population Models” illustrates how one adds more detail to a model, first through density-independent models, then by showing common matrix-model formulations and how those are used to reveal properties of structured models (e.g. population growth rate, stage/age structure). Structured population models have more detail than their nonstructured counterparts. They account for the differences among individuals within a population, usually by explicitly modeling them as distinct state variables. Elasticity analysis is introduced as a way to identify life stages that have a disproportionately large influence on population growth rate. Structured density-dependent models are briefly introduced as extensions on these models.

Benefits from Computerized Adaptive Testing as Seen in Simulation Studies

1999 ◽  
Vol 15 (2) ◽  
pp. 91-98 ◽  
Author(s):  
Lutz F. Hornke
Keyword(s):  
Measurement Error ◽  
Computerized Adaptive Testing ◽  
Test Procedure ◽  
Adaptive Testing ◽  
Parameter Estimates ◽  
Simulation Studies ◽  
Computerized Adaptive Test ◽  
Item Banks ◽  
Item Parameters ◽  
General Reliability

Summary: Item parameters for several hundreds of items were estimated based on empirical data from several thousands of subjects. The logistic one-parameter (1PL) and two-parameter (2PL) model estimates were evaluated. However, model fit showed that only a subset of items complied sufficiently, so that the remaining ones were assembled in well-fitting item banks. In several simulation studies 5000 simulated responses were generated in accordance with a computerized adaptive test procedure along with person parameters. A general reliability of .80 or a standard error of measurement of .44 was used as a stopping rule to end CAT testing. We also recorded how often each item was used by all simulees. Person-parameter estimates based on CAT correlated higher than .90 with true values simulated. For all 1PL fitting item banks most simulees used more than 20 items but less than 30 items to reach the pre-set level of measurement error. However, testing based on item banks that complied to the 2PL revealed that, on average, only 10 items were sufficient to end testing at the same measurement error level. Both clearly demonstrate the precision and economy of computerized adaptive testing. Empirical evaluations from everyday uses will show whether these trends will hold up in practice. If so, CAT will become possible and reasonable with some 150 well-calibrated 2PL items.

Measurement error and person-specific reliability in multilevel autoregressive modeling.

2019 ◽  
Vol 24 (1) ◽  
pp. 70-91 ◽  
Author(s):  
Noémi K. Schuurman ◽  
Ellen L. Hamaker
Keyword(s):  
Measurement Error ◽  
Autoregressive Modeling

Technical Memoranda. Measurement error for six port ana

1990 ◽  
Vol 137 (6) ◽  
pp. 415 ◽  
Author(s):  
E. Bergeault ◽  
B. Huyart ◽  
G. Geneves ◽  
L. Jallet
Keyword(s):  
Measurement Error

Zirconia thickness measurements for irradiated fuel rods: an approach to better understanding measurement error

2011 ◽  
pp. 107-114
Author(s):  
B. Lacroix ◽  
T. Martella ◽  
M. Pras ◽  
M. Masson-Fauchier ◽  
L. Fayette
Keyword(s):  
Measurement Error ◽  
Fuel Rods ◽  
Thickness Measurements ◽  
Irradiated Fuel

Plasminogen Depletion during Streptokinase Treatment or Two-Chain Urokinase Incubation Correlates with Decreased Clot Lysability Ex Vivo and In Vitro

1993 ◽  
Vol 70 (06) ◽  
pp. 0998-1004 ◽  
Author(s):  
Páll T Önundarson ◽  
H Magnús Haraldsson ◽  
Lena Bergmann ◽  
Charles W Francis ◽  
Victor J Marder
Keyword(s):  
Myocardial Infarction ◽  
Ex Vivo ◽  
Time Dependent ◽  
State Variables ◽  
Thrombolytic Treatment ◽  
Direct Proportion ◽  
Plasmin Activity ◽  
Plasma Exposure ◽  
The Relationship

SummaryThe relationship between lytic state variables and ex vivo clot lysability was investigated in blood drawn from patients during streptokinase administration for acute myocardial infarction. A lytic state was already evident after 5 min of treatment and after 20 min the plasminogen concentration had decreased to 24%, antiplasmin to 7% and fibrinogen 0.2 g/1. Lysis of radiolabeled retracted clots in the patient plasmas decreased from 37 ± 8% after 5 min to 21 ± 8% at 10 min and was significantly lower (8 ± 9%, p <0.005) in samples drawn at 20, 40 and 80 min. Clot lysability correlated positively with the plasminogen concentration (r = 0.78, p = 0.003), but not with plasmin activity. Suspension of radiolabeled clots in normal plasma pre-exposed to 250 U/ml two-chain urokinase for varying time to induce an in vitro lytic state was also associated with decreasing clot lysability in direct proportion with the duration of prior plasma exposure to urokinase. The decreased lysability correlated with the time-dependent reduction in plasminogen concentration (r = 0.88, p <0.0005). Thus, clot lysability decreases in conjunction with the development of the lytic state and the associated plasminogen depletion. The lytic state may therefore limit reperfusion during thrombolytic treatment.

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