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Chem. Analysis > L2: Sampling > Flashcards

L2: Sampling Flashcards

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1
Q

Sampling

A

selecting units from a population to estimate its characteristics

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2
Q

Population

A

Aggregate of units under examination

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3
Q

Why sample?

A

very large population or if investigation is destructive, expensive, time consuming, and labourious

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4
Q

Random Sampling

A

units are selected randomly (purest form of probability sampling, each member has an equal chance of being selected)

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5
Q

Stratified Sampling

A

When population is split into several groups of units, called strata, based on characteristics. Units are randomly selected from each stratum.

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6
Q

Systematic Sampling

A

First unit selected randomly, then consecutive units are chosen at specified intervals.

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7
Q

Authoritative Sampling

A

Person makes an educated guess on which units are best to sample

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8
Q

Criteria for selecting sampling plan

A

objectives, cost, environment, patterns of environmental contamination, site considerations, public concerns

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9
Q

Parameter

A

refers to population characteristic under examination (mean, sd, etc)

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10
Q

Statistic

A

refers to sample parameters used to estimate population characteristics (sample mean, sample error)

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11
Q

Bias

A

refers to how far the average statistic lies from parameter it’s estimating (Error that occurs when estimating a quantity)

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12
Q

Sampling Distribution

A

Probability distribution, under repeated sampling (numerical quantity calculated from data values in sample)

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13
Q

Probability Distribution

A

Mathematical definition used to ascertain probability of population parameter to acquire specific value or lie within specific range of values (discrete, continuous)

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14
Q

Distribution

A

normal, t, F, x2, exponential, lognormal, bionomial, poisson

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15
Q

Random Sampling (rectangular plot)

A

choose 2 random numbers from table (U1, U2), use formulas x=XU1, y=YU2

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16
Q

Random Sampling (Circular Plot)

A

choose 2 random numbers, multiply by 360 and R (A=360*U1, r=RU2)

17
Q

Random Sampling (Composite field samples)

A

choose 10 lab samples from N number of field samples, pick random number from table t, use formula; chosen sample = t*N+1

18
Q

Random number tables

A

table of random numbers (choose random starting value; move horizontally to the right, skipping alternate numbers or move vertically down, picking every 5th number)

19
Q

Hot Spot

A

contaminated area/pocket in defined environment

20
Q

Why is systematic grid sampling preferred for locating hot spots

A

efficient in finding patterns and locating rare events; flexible and more defensible sampling designs

21
Q

Hot Spot sampling assumptions

A

assume hot spot is circular or elliptical, samples are taken on square/rectangle/triangular grid, distance between grid points are larger than sampled area

22
Q

Hot Spot considerations

A

hot spot shape, length of longest axis of hot spot, level of certainty to confirm there is no hot spots at site

23
Q

Grab Sample

A

sample collected at specific time and place

24
Q

Composite Sample

A

mixture of samples collected at different times from same sampling point (useful for observing average concentrations, saves time and money)

25
Q

Integrated Samples

A

Samples collected from different points simulaneously

26
Q

Sampling domain & unit

A

domain (watershed, lake, stream, pipe end, waste disposal site)

Neighbourhood (sampling units are divisions of sampling domain)

27
Q

Chain of Custody

A

recording all information w/ respect to the sample (purpose, location, type, method, date/time, sampler’s name, signatures, volume of sample, etc)

28
Q

Equipment/Rinsate Blanks

A

analyte-free water used to rinse sample equipment before and after it is being used

29
Q

Field Blanks

A

measures contamination during sample collection, preservation, storage, and analyses; analyte free water undergone entire process (one filed blank w/ each sample batch)

30
Q

Laboratory/Matrix blanks

A

complete matrix minus analyte of interest carried through all steps of procedure

31
Q

Reagent Blanks

A

measures contamination in any single reagent used in procedure

32
Q

Replicate Samples

A

2+ samples collected at same time and location

33
Q

Replicate analysis

A

2+ analyses of the same sample

Chem. Analysis (6 decks)

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