ASRB NET - Agricultural Statistics (and Computer Application / Bioinformatics) · India · Agricultural Scientists Recruitment Board (ICAR)
Original practice questions written to the published syllabus · not past papersCombining trials across sites and seasons: testing homogeneity of error variances, pooled analysis, genotype by environment interaction, the classical stability models and AMMI and GGE biplots that decide variety release in national coordinated trials.
In the exams: AICE-JRF Ag Stat Units 3-4 'groups of experiments', 'stability parameters' (heavy); AICE-JRF Agronomy Unit 6 'pooled analysis' (heavy); ASRB NET Ag Stat (present)
ASRB NET / ARS Agricultural Statistics
Applied MET analysis: choosing error terms, interpreting stability parameters, AMMI and GGE biplots, factor-analytic mixed models for variety testing.
How our questions for ASRB NET spread across the units of Groups of Experiments, Multi-Location Trials & Genotype x Environment Analysis. Difficulty: 13 easy, 46 medium, 27 hard.
| GGE biplots and mega-environment analysis | 11 | |
| Mixed-model analysis of multi-environment trials | 11 | |
| Finlay-Wilkinson and Eberhart-Russell stability models | 10 | |
| Other stability parameters: Shukla, Wricke's ecovalence and Perkins-Jinks | 10 | |
| Groups of experiments and testing homogeneity of error variances | 9 | |
| Pooled analysis over locations and years | 9 | |
| Genotype x environment interaction and its partitioning | 9 | |
| AMMI models | 9 | |
| Analysis of perennial and repeated-season experiments | 8 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Why did Finlay and Wilkinson analyse log yields?
B. To make proportional differences additive
On the log scale, a constant percentage advantage gives parallel lines; on the original scale it inflates slopes for high yielders.
Further reading: Gomez and Gomez, Statistical Procedures for Agricultural Research; Kang and Gauch, Genotype-by-Environment Interaction
For 10 genotypes and 6 environments, after IPCA1 (13 df), IPCA2 (11 df) and IPCA3 (9 df), how many df remain for the interaction residual?
A. 12
Interaction df = 9 x 5 = 45; 45 - 33 = 12.
Further reading: Gomez and Gomez, Statistical Procedures for Agricultural Research; Kang and Gauch, Genotype-by-Environment Interaction
What does the horizontal axis of an AMMI1 biplot usually show?
C. Genotype and environment means
AMMI1 plots main effects (means) against IPCA1 scores.
Further reading: Gomez and Gomez, Statistical Procedures for Agricultural Research; Kang and Gauch, Genotype-by-Environment Interaction
In a which-won-where view, what do the vertex genotypes of the polygon represent?
C. The best genotypes in the environments within their sectors
Perpendiculars to polygon sides define sectors; each vertex genotype wins in the environments of its sector.
Further reading: Gomez and Gomez, Statistical Procedures for Agricultural Research; Kang and Gauch, Genotype-by-Environment Interaction
Which scaling suits comparing genotypes in a GGE biplot?
A. Genotype-focused singular value partitioning
Allocating singular values to genotype scores makes genotype distances interpretable.
Further reading: Gomez and Gomez, Statistical Procedures for Agricultural Research; Kang and Gauch, Genotype-by-Environment Interaction
What is a limitation of biplots?
C. They show only two components and no standard errors
If PC1 and PC2 explain little, patterns may mislead; nearby genotypes may not differ significantly.
Further reading: Gomez and Gomez, Statistical Procedures for Agricultural Research; Kang and Gauch, Genotype-by-Environment Interaction
What allows prediction of a genotype's performance in an environment where it was not tested?
C. Genetic correlations between environments in the mixed model
BLUPs borrow from correlated environments; adequate connectivity between sites is needed.
Further reading: Gomez and Gomez, Statistical Procedures for Agricultural Research; Kang and Gauch, Genotype-by-Environment Interaction
Who proposed the stability variance statistic?
A. Shukla
Shukla (1972) proposed the stability variance; Wricke ecovalence; Gauch AMMI; Yan GGE.
Further reading: Gomez and Gomez, Statistical Procedures for Agricultural Research; Kang and Gauch, Genotype-by-Environment Interaction
How do Cornelius's F tests for AMMI axes compare with Gollob's?
D. They are more conservative and often retain fewer axes
Cornelius tests are more conservative; cross-validation may retain fewer still.
Further reading: Gomez and Gomez, Statistical Procedures for Agricultural Research; Kang and Gauch, Genotype-by-Environment Interaction
In a mixed model for repeated harvests, which structure would reveal alternate bearing?
C. A temporal structure estimating a negative between-year correlation
An AR(1) or similar structure allows a negative correlation, revealing alternate bearing.
Further reading: Gomez and Gomez, Statistical Procedures for Agricultural Research; Kang and Gauch, Genotype-by-Environment Interaction
Ten here, 86 in the app. The Laisha app has every practice question we have written to ASRB NET in this subject, marked as you go, with timed papers, a jump-to-unanswered list and a certificate when you pass at 70 per cent.
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