US federal Mathematical Statistician (series 1529) - USDA NASS and others

USA · USDA National Agricultural Statistics Service via USAJOBS (Office of Personnel Management rules) · civil-service · unverified source

67practice questions written to this syllabus
5subjects

Format

No written exam: applications are rated on qualifications (statistics coursework and degree) and experience.

Sections

Over the years

Built from Laisha's knowledge because the official page could not be opened or was not found during research (web search quota exhausted); confirm against the body's current notification before relying on it. NASS runs the US Census of Agriculture and crop and livestock surveys, including objective yield surveys.

Official source: https://www.nass.usda.gov/

Subjects this exam draws on

Exploratory Data Analysis & Statistical Graphics13 questionsAgricultural Statistics System, Census & Official Statistics10 questionsIndex Numbers, National Accounts & Agricultural Economic Statistics4 questionsCrop Forecasting, Weather-Based Models & Non-linear Growth Models3 questionsSpatial Statistics, Geostatistics & Remote Sensing for Agriculture37 questions

Five practice questions, worked

Original questions written to this exam's published syllabus and pattern. Not past papers.

1. An RBD has 8 treatments in 4 blocks. The data file contains 31 rows of plot yields. What does a first data check conclude?

  1. A plot record is missing or merged; find which before analysis
  2. One block was dropped from the experiment, leaving 3 blocks
  3. One whole block was dropped from the experiment, leaving three blocks of eight plots
  4. A treatment was added after randomisation, which accounts for the unexpected extra plots
Answer and working

A. A plot record is missing or merged; find which before analysis

The design implies 8 × 4 = 32 plots. A count of 31 shows a missing record (or a duplicate plus two missing). Counting each treatment and block finds which one.

Exploratory Data Analysis & Statistical Graphics · Types of data and measurement scales

2. Which USDA NASS publication supplies the prices-received and prices-paid indices?

  1. Grain Stocks
  2. Agricultural Prices
  3. Crop Progress
  4. Hogs and Pigs Inventory
Answer and working

B. Agricultural Prices

Monthly Agricultural Prices report.

Agricultural Statistics System, Census & Official Statistics · Agricultural prices, wages and market arrival statistics

3. Which index fails the unit (commensurability) test?

  1. The Laspeyres weighted aggregative index
  2. The simple aggregative index sum p1 / sum p0
  3. The Fisher ideal index
  4. The geometric mean of price relatives
Answer and working

B. The simple aggregative index sum p1 / sum p0

sum p1 / sum p0 changes when one commodity is priced per kilogram instead of per quintal, because absolute prices are added. Weighted aggregative formulas and means of relatives are unit-free.

Index Numbers, National Accounts & Agricultural Economic Statistics · Tests of index numbers: time reversal, factor reversal and circularity

4. In an objective yield survey of the kind run by the US national agricultural statistics service, what is collected?

  1. Satellite images classified into land cover only
  2. Plant counts and measurements in sample plots
  3. Farmers' opinions of expected price at harvest
  4. Total sales recorded by grain elevators each week
Answer and working

B. Plant counts and measurements in sample plots

Objective yield surveys lay out sample plots in fields and count and measure plants and fruit (ears, pods, bolls) to model yield, complementing farmer-reported surveys. Prices and elevator sales are not yield measurements.

Crop Forecasting, Weather-Based Models & Non-linear Growth Models · Pre-harvest forecasting: purpose and history

5. District-wise average yields of maize for all districts of a state form which type of spatial data?

  1. Areal (lattice) data
  2. Point-pattern data
  3. Marked point data
  4. Geostatistical (point-referenced) data
Answer and working

A. Areal (lattice) data

Values attached to fixed units that cover the region are areal or lattice data, analysed with spatial weights, Moran's I and SAR or CAR models.

Spatial Statistics, Geostatistics & Remote Sensing for Agriculture · Spatial data types: geostatistical, areal and point-pattern

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