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FDSC 300 > Lecture 2 - Sampling > Flashcards

Lecture 2 - Sampling Flashcards

1
Q

define sampling

A

predetermined procedure for the selection, withdrawal, preservation, transportation, and preparation of the portions to be removed from a lot as samples

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2
Q

why do we sample?

A
  • save $$$

- difficult logistics of large populations

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3
Q

the set of all objects in the system being investigated

A

population

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4
Q

a portion selected from a large quantity of material

or a unit taken from the total amount of food

A

sample

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5
Q

a sample prepared for testing or analysis

A

laboratory sample

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6
Q

a quantity of bulk material of similar composition whose properties are under study

A

lot

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7
Q

quantity of food that is known or assumed to be produced under uniform conditions

A

batch

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8
Q

each discrete, identifiable portion of food that are suitable for removal from a population as samples that can be individually describes, analyzed or combined

A

unit

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9
Q

the degree to which a property or substance is randomly distributed throughout a propulation

A

homogeneity

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10
Q

an individual portion of material collected by a single operation of a sampling device

A

increment

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11
Q

accurate sampling is important to avoid what kind of risks?

A

consumer risk, producer risk

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12
Q

what is consumer risk?

A

accepting defective product

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13
Q

what is producer risk?

A

rejecting an acceptable product

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14
Q

_____ error arises when a sample is not representative of the population

A

sampling

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15
Q

_____ error arises because of some other reasons

A

non-sampling

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16
Q

______ is an estimate of the uncertainty

A

variance

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17
Q

______ ______ is a function of the sum of variances associated with each step

A

total variance

18
Q

what are the probability sampling plans?

A
  • simple random sampling
  • stratified sampling
  • cluster sampling
  • composite sampling
  • systematic sampling
19
Q

what are non-probability sampling plans?

A
  • judgment sampling
  • convenience sampling
  • restricted sampling
  • quota sampling
20
Q

every unit in a population having a known and equal chance of being selective is representative of what category of sampling plan?

A

probability sampling plan

21
Q

what motivates the use of a probability sampling plan? (4)

A
  • provides statistically sound basis for obtaining representative samples
  • eliminate human bias
  • scientific, operationally convenient and simple in theory
  • best methods to achieve a representative sample
22
Q

describe simple random sampling

A
  • population N must be known
  • random selection process
    ~ simple, high prob of being representative
    ~ IDing all units of the pop can be difficult
23
Q

describe stratified sampling

A
  • divides pop into mutually exclusive subgroups then uses simple random sampling to choose units from each stratum
    ~ more homogenous data, administrative convenience, lower cost, smaller variances for sample sizes
    ~ potential classification error
    ~ prior knowledge of composition and distribution of population; tedious
24
Q

describe cluster sampling

A
  • pop divided into clusters designed to be as similar as possible; randomly selected clusters sampled
    ~ less costly than simple/stratified
    ~ higher sampling error
25
Q

describe systematic sampling

A
  • first unit selected at random from the first k population units and then units are taken every nth unit
    ~ highly representative, very informational
    ~ not as random
26
Q

describe composite sampling

A
  • samples drawn from different units in a pop are pooled for analysis
27
Q

the technique where the odds of any unit being selected for a sample cannot be calculated since the selection is based on nonrandom procedures refers to _____ sampling plans

A

non-probability

28
Q

when would non-probability sampling be appropriate?

A

checking for adulteration

29
Q

describe judgment sampling

A

dependent on subjective judgment of the person who is drawing the samples

30
Q

describe convenience sampling

A
  • selecting only accessible part of pop

- aka chunk or grab sampling

31
Q

describe restricted sampling

A

used when the entire pop is not accessible

32
Q

describe quota sampling

A
  • pop divided into groups; samples are chosen based on experience and judgment
    (sampling from groups representing various categories)
33
Q

what 4 factors affect the choice of sampling plan?

A
  • purpose of inspection
  • nature of population
  • nature of product
  • nature of test method
34
Q

what’s attribute sampling?

A
  • based on whether or not sample possess a certain characteristic (discrete)
35
Q

what’s variance sampling?

A
  • estimate quantitatively the amount of a substance or a characteristic (continuous)
36
Q

what type of sampling is this: trained person randomly picks sample/location from sample lot/liquid container as specified by the approved standard method

A

manual sampling

37
Q

what type of sampling is this: performed mechanically

A

continuous sampling

38
Q

what 3 criteria determine sample size?

A
  • level of precision
  • level of confidence (risk)
  • degree of variability among the population for the attributes beingmeasured
39
Q

write the sample size formula for an unknown population

A

okay

40
Q

write the sample size formula for a known population

A

aight

FDSC 300 (6 decks)

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