Lecture 2 - Sampling Flashcards Preview

FDSC 300 > Lecture 2 - Sampling > Flashcards

Flashcards in Lecture 2 - Sampling Deck (40)
Loading flashcards...
1

define sampling

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

2

why do we sample?

- save $$$
- difficult logistics of large populations

3

the set of all objects in the system being investigated

population

4

a portion selected from a large quantity of material

or a unit taken from the total amount of food

sample

5

a sample prepared for testing or analysis

laboratory sample

6

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

lot

7

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

batch

8

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

unit

9

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

homogeneity

10

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

increment

11

accurate sampling is important to avoid what kind of risks?

consumer risk, producer risk

12

what is consumer risk?

accepting defective product

13

what is producer risk?

rejecting an acceptable product

14

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

sampling

15

_____ error arises because of some other reasons

non-sampling

16

______ is an estimate of the uncertainty

variance

17

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

total variance

18

what are the probability sampling plans?

- simple random sampling
- stratified sampling
- cluster sampling
- composite sampling
- systematic sampling

19

what are non-probability sampling plans?

- judgment sampling
- convenience sampling
- restricted sampling
- quota sampling

20

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

probability sampling plan

21

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

- 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

describe simple random sampling

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

23

describe stratified sampling

- 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

describe cluster sampling

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

25

describe systematic sampling

- 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

describe composite sampling

- samples drawn from different units in a pop are pooled for analysis

27

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

non-probability

28

when would non-probability sampling be appropriate?

checking for adulteration

29

describe judgment sampling

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

30

describe convenience sampling

- selecting only accessible part of pop
- aka chunk or grab sampling