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ICAR-IASRI MSc and PhD Statistical Consulting, Research Methodology & Scientific Communication: practice questions

ICAR-IASRI MSc and PhD (Agricultural Statistics, Computer Application, Bioinformatics) · India · ICAR-Indian Agricultural Statistics Research Institute with the IARI Graduate School

Original practice questions written to the published syllabus · not past papers
10worked here, free
28written to this exam in this subject
11syllabus units

What this subject covers

The statistician as research partner: framing the scientist's question, choosing design and sample size, power, avoiding pseudo-replication, pre-registration, analysis plans, reporting standards, the p-value debate, ethics, and writing and presenting results. Research-methodology courses in the Agribusiness and Veterinary tracks cover the social-science and clinical sides.

In the exams: Present in AICE-JRF research-methodology units of other subjects; ASRB ARS interview (reported); professional accreditation (RSS CStat, ASA PStat) evidence of practice (heavy)

Where the 28 questions fall

How our questions for ICAR-IASRI MSc and PhD spread across the units of Statistical Consulting, Research Methodology & Scientific Communication. Difficulty: 16 easy, 12 medium, 0 hard.

Power and sample size for experiments and surveys4
Choosing the experimental or sampling unit3
Analysis plans and pre-registration3
Common errors in agricultural research: pseudo-replication and multiple testing3
Reporting standards for experiments and surveys3
Writing theses, papers and technical reports3
P-values, confidence intervals and the ASA statement on p-values2
Research ethics, data integrity and authorship2
Presenting statistical results to non-statisticians2
Project proposals and research funding2
The consulting interview: from scientific question to statistical question1

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 · Choosing the experimental or sampling unit · easy

A useful question for identifying the experimental unit is:

  1. How many measurements were taken?
  2. Which software was used?
  3. What was randomised to what?
  4. Who funded the study?
Answer and working

C. What was randomised to what?

The unit of randomisation defines the experimental unit.

Further reading: Hurlbert (1984); Wasserstein and Lazar, ASA statement on p-values (2016); Mead, Gilmour and Mead, Statistical Principles for the Design of Experiments (2012); Cabrera and McDougall, Statistical Consulting (2002)

2 · Power and sample size for experiments and surveys · medium

A cluster survey has design effect 2. Compared with simple random sampling, the sample needed for the same precision is:

  1. Half as large
  2. The same
  3. Four times as large
  4. Twice as large
Answer and working

D. Twice as large

Multiply the SRS size by deff.

Further reading: Hurlbert (1984); Wasserstein and Lazar, ASA statement on p-values (2016); Mead, Gilmour and Mead, Statistical Principles for the Design of Experiments (2012); Cabrera and McDougall, Statistical Consulting (2002)

3 · Power and sample size for experiments and surveys · medium

For a randomised block design with many treatments and blocks, power is most flexibly obtained by:

  1. Using the two-sample formula only, ignoring the blocks
  2. Guessing from previous papers
  3. Simulation of the planned design
  4. Assuming power is always 80%
Answer and working

C. Simulation of the planned design

Simulation handles complex structures.

Further reading: Hurlbert (1984); Wasserstein and Lazar, ASA statement on p-values (2016); Mead, Gilmour and Mead, Statistical Principles for the Design of Experiments (2012); Cabrera and McDougall, Statistical Consulting (2002)

4 · Analysis plans and pre-registration · easy

Writing an analysis plan early often:

  1. Guarantees publication in a journal of the authors' choice
  2. Makes data collection unnecessary
  3. Fixes the p-value in advance
  4. Reveals design problems early
Answer and working

D. Reveals design problems early

Planning the analysis tests the design.

Further reading: Hurlbert (1984); Wasserstein and Lazar, ASA statement on p-values (2016); Mead, Gilmour and Mead, Statistical Principles for the Design of Experiments (2012); Cabrera and McDougall, Statistical Consulting (2002)

5 · Common errors in agricultural research: pseudo-replication and multiple testing · easy

Hurlbert's 1984 term for treating non-independent subsamples as replicates is:

  1. Randomisation
  2. Pseudo-replication
  3. Blocking
  4. Stratification
Answer and working

B. Pseudo-replication

It inflates apparent significance.

Further reading: Hurlbert (1984); Wasserstein and Lazar, ASA statement on p-values (2016); Mead, Gilmour and Mead, Statistical Principles for the Design of Experiments (2012); Cabrera and McDougall, Statistical Consulting (2002)

6 · Reporting standards for experiments and surveys · easy

Reporting guidelines exist mainly because:

  1. Journals want longer papers and more pages of text
  2. They replace peer review
  3. They guarantee significance
  4. Many reports omit essentials
Answer and working

D. Many reports omit essentials

Missing details prevent evaluation and replication.

Further reading: Hurlbert (1984); Wasserstein and Lazar, ASA statement on p-values (2016); Mead, Gilmour and Mead, Statistical Principles for the Design of Experiments (2012); Cabrera and McDougall, Statistical Consulting (2002)

7 · Writing theses, papers and technical reports · medium

Error bars in a figure must be:

  1. Omitted to save space in crowded figures (by default)
  2. Defined in the caption
  3. Always standard deviations
  4. Coloured red
Answer and working

B. Defined in the caption

Readers cannot interpret undefined bars.

Further reading: Hurlbert (1984); Wasserstein and Lazar, ASA statement on p-values (2016); Mead, Gilmour and Mead, Statistical Principles for the Design of Experiments (2012); Cabrera and McDougall, Statistical Consulting (2002)

8 · Presenting statistical results to non-statisticians · medium

Replacing 'significant at p < 0.05' when speaking to farmers, a better statement is:

  1. How big, and how sure
  2. 'The p-value was small, so the effect is real'
  3. 'It passed the test'
  4. 'Statistically robust'
Answer and working

A. How big, and how sure

Size and certainty matter for decisions.

Further reading: Hurlbert (1984); Wasserstein and Lazar, ASA statement on p-values (2016); Mead, Gilmour and Mead, Statistical Principles for the Design of Experiments (2012); Cabrera and McDougall, Statistical Consulting (2002)

9 · Project proposals and research funding · easy

Objectives in a research proposal should be:

  1. SMART
  2. As broad as possible, to cover any result
  3. Identical to the title
  4. Free of any measurable target
Answer and working

A. SMART

SMART objectives can be evaluated.

Further reading: Hurlbert (1984); Wasserstein and Lazar, ASA statement on p-values (2016); Mead, Gilmour and Mead, Statistical Principles for the Design of Experiments (2012); Cabrera and McDougall, Statistical Consulting (2002)

10 · Project proposals and research funding · medium

A theory of change describes:

  1. The statistical model to be fitted to the data
  2. How a project leads to impact
  3. The randomisation scheme
  4. The data format
Answer and working

B. How a project leads to impact

Funders use it alongside logframes.

Further reading: Hurlbert (1984); Wasserstein and Lazar, ASA statement on p-values (2016); Mead, Gilmour and Mead, Statistical Principles for the Design of Experiments (2012); Cabrera and McDougall, Statistical Consulting (2002)

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Read the subject

Statistical Consulting, Research Methodology & Scientific CommunicationThe full study manual, free ICAR-IASRI MSc and PhDFormat, sections and how it has changed

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