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ICAR AICE-JRF/SRF Data Analysis with Statistical Software & Reproducible Research: practice questions

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 papers
10worked here, free
24written to this exam in this subject
9syllabus units

What this subject covers

Running real analyses in R, SAS, SPSS, Python and Genstat: importing and managing agricultural data, running designed-experiment, survey and genetics analyses, checking outputs, and making the work reproducible with scripts, literate documents and version control. Includes spreadsheet analysis tools that AIEEA-PG names.

In the exams: AIEEA-PG Group 07 'Excel data analysis tools, correlation and regression, t-test and one-way ANOVA' (heavy); AICE-JRF Ag Stat (applied); SAS certifications (heavy)

Where the 24 questions fall

How our questions for ICAR AICE-JRF/SRF spread across the units of Data Analysis with Statistical Software & Reproducible Research. Difficulty: 3 easy, 15 medium, 6 hard.

R for designed experiments: aov, lm, emmeans and agricolae4
Genstat and specialist software for agricultural research4
Survey analysis software: design-based estimation with weights4
SAS: PROC GLM, MIXED, REG and SURVEYMEANS3
Web-based statistical computing portals for agricultural researchers3
Literate programming: R Markdown, Quarto and notebooks2
Version control with Git2
SPSS and point-and-click tools: uses and limits1
Data management: cleaning, validation and metadata1

10 practice questions, worked

Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.

1 · SAS: PROC GLM, MIXED, REG and SURVEYMEANS · hard

For a split plot in blocks analysed with PROC MIXED, the random effects are specified as:

  1. RANDOM block block*A;
  2. MODEL block A;
  3. REPEATED A;
  4. CLASS block;
Answer and working

A. RANDOM block block*A;

Block and the main-plot error (block × A) are random.

Further reading: Welham et al., Statistical Methods in Biology (2015); Littell et al., SAS for Mixed Models (2006); Lumley, Complex Surveys (2010); Chacon and Straub, Pro Git (2014)

2 · SAS: PROC GLM, MIXED, REG and SURVEYMEANS · medium

PROC GLIMMIX extends PROC MIXED to:

  1. Survey weights only
  2. Data cleaning
  3. Version control
  4. Non-normal mixed models
Answer and working

D. Non-normal mixed models

Counts and proportions are modelled with link functions.

Further reading: Welham et al., Statistical Methods in Biology (2015); Littell et al., SAS for Mixed Models (2006); Lumley, Complex Surveys (2010); Chacon and Straub, Pro Git (2014)

3 · Genstat and specialist software for agricultural research · easy

REML for unbalanced mixed models was derived by Patterson and Thompson in:

  1. 1925
  2. 1990
  3. 2005
  4. 1971
Answer and working

D. 1971

It allows recovery of inter-block information with unequal block sizes.

Further reading: Welham et al., Statistical Methods in Biology (2015); Littell et al., SAS for Mixed Models (2006); Lumley, Complex Surveys (2010); Chacon and Straub, Pro Git (2014)

4 · Genstat and specialist software for agricultural research · hard

Separable AR(1) × AR(1) models in field-trial analysis describe:

  1. Correlation between surveys
  2. Random seeds
  3. Treatment structure
  4. Row and column spatial correlation
Answer and working

D. Row and column spatial correlation

Neighbouring plots are correlated in both directions.

Further reading: Welham et al., Statistical Methods in Biology (2015); Littell et al., SAS for Mixed Models (2006); Lumley, Complex Surveys (2010); Chacon and Straub, Pro Git (2014)

5 · Survey analysis software: design-based estimation with weights · hard

A stratum containing a single PSU causes a problem because:

  1. Its weight becomes zero in every estimate
  2. It must be deleted
  3. Its variance is not estimable
  4. It doubles the mean
Answer and working

C. Its variance is not estimable

Strata are collapsed or special options used.

Further reading: Welham et al., Statistical Methods in Biology (2015); Littell et al., SAS for Mixed Models (2006); Lumley, Complex Surveys (2010); Chacon and Straub, Pro Git (2014)

6 · Literate programming: R Markdown, Quarto and notebooks · medium

A parameterised report is useful for a multi-location trial because it:

  1. Combines all sites into one number
  2. Renders one template for each site
  3. Removes the need for analysis
  4. Hides site differences
Answer and working

B. Renders one template for each site

Routine reporting becomes efficient and consistent.

Further reading: Welham et al., Statistical Methods in Biology (2015); Littell et al., SAS for Mixed Models (2006); Lumley, Complex Surveys (2010); Chacon and Straub, Pro Git (2014)

7 · Literate programming: R Markdown, Quarto and notebooks · medium

Caching long computations in a dynamic document requires care that:

  1. Caches are never cleared once they have been made
  2. Caches are refreshed when inputs change
  3. The data are deleted
  4. Seeds are removed
Answer and working

B. Caches are refreshed when inputs change

Stale caches give outdated results.

Further reading: Welham et al., Statistical Methods in Biology (2015); Littell et al., SAS for Mixed Models (2006); Lumley, Complex Surveys (2010); Chacon and Straub, Pro Git (2014)

8 · Version control with Git · medium

Committing a password to a repository is serious mainly because:

  1. It slows the repository down for every user
  2. It changes the code
  3. It persists in the history
  4. It breaks branches
Answer and working

C. It persists in the history

Even deleted files remain in earlier commits.

Further reading: Welham et al., Statistical Methods in Biology (2015); Littell et al., SAS for Mixed Models (2006); Lumley, Complex Surveys (2010); Chacon and Straub, Pro Git (2014)

9 · Web-based statistical computing portals for agricultural researchers · medium

A quick plausibility check of a portal's ANOVA output is to verify:

  1. The colour scheme
  2. The server location
  3. The page title
  4. The error degrees of freedom
Answer and working

D. The error degrees of freedom

Wrong df reveal a mis-specified design.

Further reading: Welham et al., Statistical Methods in Biology (2015); Littell et al., SAS for Mixed Models (2006); Lumley, Complex Surveys (2010); Chacon and Straub, Pro Git (2014)

10 · Web-based statistical computing portals for agricultural researchers · hard

An experiment with repeated measurements over time on each plot is analysed in a portal offering only one-time RCBD analysis. The likely error is:

  1. Overestimating the block effect in every case
  2. Repeated measures treated as independent
  3. Using the wrong seed
  4. Reporting too many decimals
Answer and working

B. Repeated measures treated as independent

Correlation within plots over time must be modelled.

Further reading: Welham et al., Statistical Methods in Biology (2015); Littell et al., SAS for Mixed Models (2006); Lumley, Complex Surveys (2010); Chacon and Straub, Pro Git (2014)

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Read the subject

Data Analysis with Statistical Software & Reproducible ResearchThe full study manual, free ICAR AICE-JRF/SRFFormat, sections and how it has changed

More ICAR AICE-JRF/SRF practice

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