ICAR AICE-JRF/SRF - Agricultural Statistics, Computer Application, Bioinformatics (PhD admission and fellowship) · India · National Testing Agency for ICAR
Original practice questions written to the published syllabus · not past papersStudying several factors at once: 2^n, 3^n and asymmetrical factorials, main effects and interactions by Yates' method, total and partial confounding, fractional factorials, and the split-plot, split-split-plot and strip-plot layouts that field operations such as irrigation and tillage force on agronomists.
In the exams: AICE-JRF Ag Stat Unit 4 (heavy: 2^n, 3^n, asymmetrical, confounding, split, strip and crossover named); AICE-JRF Agronomy Unit 6 (heavy); ASRB NET Ag Stat (heavy)
ICAR AICE-JRF/SRF Agricultural Statistics (Unit 4)
2^n and 3^n factorials, asymmetrical factorials, total and partial confounding, split- and strip-plot designs, crossover designs: effects, sums of squares, confounding schemes, degrees of freedom and error terms.
ICAR AICE-JRF/SRF Agronomy (Unit 6) and other crop subjects
Split-plot, strip-plot, factorial and simple confounding designs as used in agronomic research; which design for which practical constraint; reading the ANOVA.
How our questions for ICAR AICE-JRF/SRF spread across the units of Factorial Experiments, Confounding, Split- & Strip-Plot Designs. Difficulty: 21 easy, 50 medium, 17 hard.
| Factorial experiments: main effects and interactions | 11 | |
| 2^n factorials and Yates' algorithm | 10 | |
| Total and partial confounding | 10 | |
| Split-plot designs and their error terms | 10 | |
| Fractional factorials and aliasing | 9 | |
| Crossover (changeover) designs | 8 | |
| 3^n factorials | 7 | |
| Asymmetrical factorials | 6 | |
| Strip-plot (split-block) designs | 6 | |
| Factorials with extra (control) treatments | 6 | |
| Split-split-plot designs | 5 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
In a 3 x 4 factorial (A at 3 levels, B at 4) in an RCBD with 3 replications and error mean square MSE, what is the standard error of the difference between two A means?
C. The square root of (2 MSE / 12)
Each A mean is averaged over r x b = 3 x 4 = 12 plots, so SEd = sqrt(2 MSE / 12). The square root of 2 MSE / 3 is for two treatment-combination means; 2 MSE / 9 would be for B means (r x a = 9).
Further reading: Cochran and Cox, Experimental Designs; Gomez and Gomez, Statistical Procedures for Agricultural Research
Confounding AB and ABC in a 2^3 in four blocks of two would be a bad choice because:
D. Their generalised interaction C, a main effect, is also confounded
(AB)(ABC) = A^2B^2C = C, so the main effect of C would be lost. Confounded effects should be chosen so that their generalised interactions are high-order.
Further reading: Cochran and Cox, Experimental Designs; Gomez and Gomez, Statistical Procedures for Agricultural Research
What is the resolution of a 2^(4-1) design with defining relation I = ABCD?
C. IV
Resolution is the length of the shortest word in the defining relation; ABCD has four letters, so resolution IV: main effects are clear of two-factor interactions, but two-factor interactions are aliased with each other.
Further reading: Cochran and Cox, Experimental Designs; Gomez and Gomez, Statistical Procedures for Agricultural Research
A significant contrast in a 2^(4-1) (I = ABCD) estimates AC + BD. How can the two effects be separated?
D. Run the complementary or fold-over fraction
Replicating the same fraction keeps AC and BD aliased; running the other half (or a fold-over) breaks the alias. Subject knowledge may also suggest which is plausible.
Further reading: Cochran and Cox, Experimental Designs; Gomez and Gomez, Statistical Procedures for Agricultural Research
How are the two factors randomised in a strip-plot design?
A. Each factor is randomised to its strips independently in every block
Horizontal strips get factor A at random and vertical strips get factor B at random, separately in each block; randomising B within A plots would be a split plot.
Further reading: Cochran and Cox, Experimental Designs; Gomez and Gomez, Statistical Procedures for Agricultural Research
A 3 x 3 factorial plus one control is in an RCBD. How are the 9 treatment degrees of freedom split?
D. Control vs rest 1, A 2, B 2, A x B 4
Ten treatments give 9 df: one for control versus the nine factorial combinations and 8 for the 3 x 3 factorial (2 + 2 + 4).
Further reading: Cochran and Cox, Experimental Designs; Gomez and Gomez, Statistical Procedures for Agricultural Research
A 2 x 2 factorial plus one control in an RCBD with 4 replications: how many error degrees of freedom are there?
C. 12
Five treatments and 4 blocks: error df = (4 - 1)(5 - 1) = 12. 9 would be the 2 x 2 alone.
Further reading: Cochran and Cox, Experimental Designs; Gomez and Gomez, Statistical Procedures for Agricultural Research
In a crossover design, each experimental unit:
B. Receives a sequence of different treatments in successive periods
Treatments are compared within units over periods, which removes between-animal variation from comparisons.
Further reading: Cochran and Cox, Experimental Designs; Gomez and Gomez, Statistical Procedures for Agricultural Research
Why are crossover designs efficient in animal experiments?
B. Between-animal variation is removed from treatment comparisons
Each animal serves as its own control, so large differences between animals do not enter the error; this is why fewer animals are needed.
Further reading: Cochran and Cox, Experimental Designs; Gomez and Gomez, Statistical Procedures for Agricultural Research
A factorial set of treatments can be laid out in which designs?
B. Any basic design: CRD, RCBD or Latin square
A factorial is a treatment structure; the combinations are arranged in whatever design suits the experimental material.
Further reading: Cochran and Cox, Experimental Designs; Gomez and Gomez, Statistical Procedures for Agricultural Research
Ten here, 88 in the app. The Laisha app has every practice question we have written to ICAR AICE-JRF/SRF 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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