Statistics Flashcards

1
Q

What is a census?

A

Measures every member of a population

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2
Q

What is a sample?

A

Observations taken from a subset of a population to get information about the whole.

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3
Q

Advantages of census

A

Completely accurate

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4
Q

Disadvantages of census

A

Time and money consuming, impossible if process involves destroying the subject, hard to process loads of data

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5
Q

Advantages sample

A

Less data, less time and money consuming, less subjects needed.

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6
Q

Disadvantages sample

A

May not be accurate, not large enough

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7
Q

Simple random sampling

A

Assign number to each unit then randomly pick

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8
Q

Systematic sampling

A

Chosen at regular intervals through a list with the position of where you start random

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9
Q

Stratified sampling

A

Proportionally picked from each group

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10
Q

Advantages of simple random sampling

A

No bias, easy/cheap

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11
Q

Disadvantages of random sampling

A

Not suitable for large groups, sampling frame required

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12
Q

Systematic sampling advantages

A

Simple, quick, good for large groups

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13
Q

Systematic sampling disadvantages

A

Sampling frame needed, can introduce bias if frame is not random

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14
Q

Stratified sampling advantages

A

Accurately represents population structure, guarantees that proportional representation

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15
Q

Stratified sampling disadvantages

A

Must be pre-classified into strata, selection has same issues as simple random sampling.

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16
Q

Quota sampling

A

Sampler selects which group the person is put in and ignores when quota is full

17
Q

Opportunity sampling

A

Take a sample if the unit suits criteria and is available

18
Q

Quota sampling advantages

A

Small sample still representative, no frame

19
Q

Quota sampling disadvantages

A

Can be biased, division into groups may be inaccurate and costly

20
Q

Opportunity sample advantages

A

Easy, cheap

21
Q

Opportunity sampling disadvantages

A

Dependent on sampler and unlikely to give representative sample

22
Q

Measure of location

A

Value that describes a position in a data set

23
Q

Measure of central tendency

A

Single value describing the centre of the data (mean, median, mode)

24
Q

When working out lower and upper quartiles how do you round?

25
Histograms
Frequency density = frequency/class width
26
Bivariate data
Pairs of values for two variables (one independent and one dependent variable)
27
What is the least squares regression line?
Line of best fit
28
Discrete uniform distribution
The probability of each outcome is the same (e.g. a fair die)
29
Conditions for binomial distribution
Fixed number of trials, two possible outcomes, fixed probability, independent
30
How to measure outliers?
1.5 x IQR below/above LQ/UQ
31
How to check whether two events are independent?
P(A and B) = P(A) × P(B) if independent
32