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A-Level Maths > Data collection > Flashcards

Data collection Flashcards

1
Q

population definition

A

complete set of individual items you are interested in

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2
Q

census definition

A

measure value from every member of a population

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3
Q

sample definition

A

selection of observations taken from a subset of the population used to try find out information about whole population

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4
Q

adv of census

A

completely accurate view of population

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5
Q

disadv of census

A

time consuming
expensive
not possible if population constantly changes
not to be used if testing process destroys items

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6
Q

adv of sample

A

less time consuming + cheaper than census

fewer people have to respond

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7
Q

disadv of sample

A

data may not be representative of population

sample may not be large enough to give info about small minority of population

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8
Q

what causes different conclusions in different samples

A

natural variation

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9
Q

how to increase validity of conclusions from sample

A

increase sample size

requires more resources

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10
Q

sampling unit definition

A

individual item of population

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11
Q

sampling element definition

A

individual item of unit

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12
Q

parameter definition

A

number describing entire population

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13
Q

statistic definition

A

number taken from a single sample

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14
Q

sampling frame definition

A

list of sampling units of population individually named

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15
Q

random sampling features

A

every member of population has equal change of being selected
removes bias from sample
should be representative of population
includes simple random, systematic, stratified sampling

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16
Q

simple random sampling features

A

every member of population has equal change of being selected
chosen at random (lottery sampling, random number generator)
needs sampling frame

17
Q

adv of simple random

A

considered fair
probably representative of population
each sampling unit has same change of being chosen

18
Q

disadv of simple random

A

not possible without sampling frame
could be time-consuming, disruptive, expensive if population large
minority groups may be missed

19
Q

systematic sampling features

A

choose starting point
select objects a certain number apart
only random of sampling frame has no order

20
Q

adv of systematic

A

quick and easy to use

suitable for large samples/populations

21
Q

disadv of systematic

A

not possible without sampling frame
may be missing values in population
sampling technique may coincide with periodic trait, no longer representative (bias)

22
Q

stratified sampling features

A

population split into distinctly different groups (strata/stratum) that cover entire population
sample chosen in each group proportionate to frequency of group in population

23
Q

adv of stratified sampling

A

minimises sample selection bias (no segment of population over/under represented)
sample reflects population
frequencies of each sample can be proportional to frequencies of each group in population

24
Q

disadv of stratified

A

requires sampling frame
strata must be carefully defined
sometimes difficult to split into naturally occurring groups

25
Q

biased sample definition

A

sample doesn’t represent population

26
Q

non-random sampling methods

A

opportunistic sampling

quota sampling

27
Q

opportunity sampling features

A

taking sample from target population available at the time

28
Q

adv of opportunistic

A

easy to select sample
inexpensive
don’t need sampling frame

29
Q

disadv of opportunistic

A

unlikely to produce sample representative of population

highly dependent on individual researcher (may not talk to mean member of target population)

30
Q

quota sampling features

A

population split into groups (strata/stratum)
size of group in sample reflects their frequency in population
judgement used to selected members from each group until quota is filled (introduced bias)

31
Q

adv of quota

A

sample should be representative of population
don’t need sampling frame
quick, easy, inexpensive
different groups’ responses can be compared

32
Q

disadv of quota

A

non-random (could be biased)
have to be split into groups (may be difficult, time consuming)
non-responses (target population member not part of sample as quota filled) not recorded (may distort interpretation)

33
Q

continuous variable definition

A

can take any value in a given range

34
Q

quantitative variable definition

A

data associated with numerical observations

35
Q

qualitative variable definition

A

data associated with non-numerical observations

have to count

36
Q

discrete variable definition

A

can only take specific values in a given range

have to measure

37
Q

knots in miles per hour

A

1 kn = 1.15 mph

A-Level Maths (5 decks)

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