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Maths Edexcel A Level > AS Statistics > Flashcards

AS Statistics Flashcards

1
Q

Population

A

The whole set of items that are of interest

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2
Q

Census

A

Observes or measures every member of a population

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3
Q

Sample

A

A selection of observations taken from a subset of the population which is used to find out information about the population as a whole

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4
Q

Sampling frame

A

List of sampling units, with each unit given an identifying name or number

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5
Q

Advantages/disadvantages of a census

A

Advantages:
Completely accurate result
Disadvantages:
Time consuming, expensive, cannot be used when testing process destroys the item, hard to process large quantity of data

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6
Q

Sample advantages/ disadvantages

A

Advantages:
Less time consuming/expensive, fewer people have to respond, less data to process than in a census
Disadvantages:
Data may not be as accurate, sample may not be large enough to give data about small subgroups of the population

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7
Q

Sampling units

A

Individual units of a population

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8
Q

Simple random sample

A

Where every sample of size n has an equal chance of being selected

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9
Q

Systematic sampling

A

Required elements are chosen at regular intervals from an ordered list

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10
Q

Stratified sampling

A

Population is divided into mutually exclusive strata and a random sample is taken from each

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11
Q

Simple random sampling advantages/disadvantages

A

Advantages: free of bias, easy and cheap to implement for small samples/populations, each sampling unit has a known and equal chance of selection
Disadvantages: not suitable for large populations (time consuming, disruptive, expensive), a sampling frame is needed

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12
Q

Systematic sampling advantages/disadvantages

A

Advantages: simple and quick to use, suitable for large samples/populations
Disadvantages: a sampling frame is needed, can introduce bias if the sampling frame is not random

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13
Q

Stratified sampling advantages/disadvantages

A

Advantages: sample accurately reflects population structure, guarantees proportional representation of groups within a population.
Disadvantages: population must be classified into distinct strata, selection within each stratum suffers from same disadvantages as simple random sampling

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14
Q

Quota sampling

A

an interviewer or researcher selects a sample that reflects the characteristics of the whole population

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15
Q

Opportunity sampling

A

Consists of taking the sample from people who are available at the time the study is carried out and who fit the criteria you are looking for

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16
Q

Quota sampling advantages/disadvantages

A

Advantages: allows a small sample to still be representative of the whole population, no sampling frame required, quick, easy and inexpensive, allows for easy comparison between different groups within a population
Disadvantages: non-random sampling can introduce bias, population must be divided into groups which can be costly and inaccurate, increasing scope of study increases number of groups (adding time and expense), non-responses are not recorded as such

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17
Q

Opportunity sampling advantages/disadvantages

A

Advantages: easy to carry out, inexpensive
Disadvantages: unlikely to provide a representative sample, highly dependent on individual researcher

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18
Q

Quantitative data/variables

A

variables or data associated with numerical observations

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19
Q

Qualitative data/variables

A

variables or data associated with non-numerical observations

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20
Q

continuous variable

A

a variable that can take any value in a given range

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21
Q

discrete variable

A

a variable that can take only specific values in a given range

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22
Q

grouped frequency table (gft)

A

the specific data values are not shown but are included in groups (or classes)

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23
Q

mid-point (gft)

A

average of class boundaries

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24
Q

Daily mean temperature units

A

degrees Celsius

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25
Q

Daily total rainfall units

A

mm

Amounts less than 0.05 mm are recorded as ‘tr’ or ‘trace’

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26
Q

Daily total sunshine

A

recorded to the nearest tenth of an hour

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27
Q

Daily mean windspeed/daily maximum gust units

A

knots

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28
Q

Daily maximum relative humidity

A

Given as a percentage of air saturation with water vapour.

Above 95% gives rise to misty and foggy conditions

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29
Q

Daily mean cloud cover units

A

‘okras’ (eighths of the sky covered by cloud)

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30
Q

Daily mean visibility units

A

decametres (Dm)

31
Q

Daily mean pressure units

A

hectopascals (hPa)

32
Q

measure of location

A

a single value which describes a position in a data set

33
Q

Measure of central tendency

A

a single value which describes the centre of the data

34
Q

Mode/modal class

A

the value or class that occurs most often

35
Q

Median

A

the middle value when the data values are put in order

36
Q

Mean formula

A

sum of the values/number of values

37
Q

Lower quartile

A

one-quarter of the way through the data set

38
Q

Upper quartile

A

three-quarters of the way through the data set

39
Q

Range

A

difference between the largest and smallest values in the data set

40
Q

Interquartile range (IQR)

A

the difference between the upper and lower quartiles

41
Q

Interpercentile range

A

the difference between the values for two given percentiles

42
Q

Standard deviation

A

square root of the variance

43
Q

Coding

A

a way of simplifying statistical calculations

44
Q

Outlier

A

an extreme value that lies outside the overall pattern of the data

45
Q

Outlier common definition

A

Greater than Q3 + k(IQR)

Or less than Q1 - k(IQR)

46
Q

cleaning the data

A

the process of removing anomalies from the data

47
Q

anomalies

A

when an outlier should be removed from the data because it is clearly an error and misleading.

48
Q

frequency polygon

A

When the middle of the top of each bar in a histogram is is joined with a straight line

49
Q

frequency density equation

A

frequency/class width

50
Q

Bivariate data

A

data which has pairs of values for two variables

51
Q

Independent/explanatory variable

A

the variable controlled by the researcher (x-axis)

52
Q

Dependent/response variable

A

the variable measured by the researcher (y-axis)

53
Q

correlation

A

describes the nature of the liner relationship between two variables

54
Q

causal relationship

A

when a change in one variable causes a change in the other
(Correlation does not mean causation!)
You need to use context of question and common sense to determine this

55
Q

experiment

A

a repeatable process that gives rise to a number of outcomes

56
Q

event

A

a collection of one or more outcomes

57
Q

sample space

A

the set of all possible outcomes

58
Q

mutually exclusive

A

when events have no outcomes in common

59
Q

Addition rule (probability)

A

For mutually exclusive events:

P(A or B) = P(A) + P(B)

60
Q

Independent

A

when one event has no effect on another

61
Q

Multiplication rule (probability)

A

P(A and B) = P(A) x P(B)

62
Q

tree diagram

A

can be used to show the outcomes of two or more events happening in succession

63
Q

random variable

A

a variable whose value depends on the outcome of a random event

64
Q

Sample space

A

the range of values that a random variable can take

65
Q

probability distribution

A

fully describes the probability of any outcome in the sample space

66
Q

discrete uniform distribution

A

when all of the probabilities are the same

67
Q

Sum of the probabilities of all outcomes of an event add up to 1

A

ΣP(X=x) = 1

68
Q

test statistic

A

the result fo the experiment or the statistic that is calculated

69
Q

null hypothesis, H0

A

the one you assume to be correct

70
Q

alternative hypothesis, H1

A

tells you about the parameter if your assumption is wrong

71
Q

critical region

A

region of the probability distribution which, if the test statistic falls within it, would cause you to reject the null hypothesis

72
Q

critical value

A

first value to fall inside the critical region

73
Q

actual significance level

A

probability of incorrectly rejecting the null hypothesis

Maths Edexcel A Level (3 decks)

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