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A-Level Maths > Stats Year 1 > Flashcards

Stats Year 1 Flashcards

1
Q

What is a population?

A

The whole set of items that are of interest

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2
Q

What is a sample?

A

The subset of the population intended to represent the population

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3
Q

What is a sampling unit?

A

Each individual thing in the population that can be sampled

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4
Q

What is a sampling frame?

A

A list of all of the sampling units

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5
Q

What is a census?

A

Data collected from the entire population

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6
Q

What are the advantages of a census?

A

Completely accurate/reliable

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7
Q

What are the disadvantages of a census?

A

Time consuming
Expensive
Large amount of data to process
Can not be used when testing involves destruction

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8
Q

What is qualitative data?

A

Non numerical values

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9
Q

What is quantitative data?

A

Numerical values

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10
Q

What is discrete data?

A

Can only take specific values

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11
Q

What is continuous data?

A

Can take any decimal values

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12
Q

How do you carry out a simple random sample?

A

-list all members of the population and assign them a number from 1-n
-use a random number generator to select k unique numbers
-select the corresponding members of the population which match the generated numbers to form the sample

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13
Q

What are the advantages of a simple random sample?

A

Easy/cheap
Each number has a known equal chance of being selected
Bias free

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14
Q

What are the disadvantages of simple random sampling?

A

Sampling frame needed
Not suitable when population is large

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15
Q

How do you carry out a systematic sample?

A

-take every K’th elements where
K=population size/sample size
-list all the members of the population and assign them a number from 1-n
-use a random number generator to select a number from 1-k as a starting point
-then select every k’th person to form the sample

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16
Q

What are the advantages of a systematic sample?

A

Simple and quick
Suitable for large samples

17
Q

What are the disadvantages of systematic sampling?

A

Sample frame needed
Can introduce bias if sampling frame not random

18
Q

How do you carry out a stratified sample?

A

-For each strata calculate…
(Size of strata/population size) x sample size
-then carry out a simple random sample for each strata
-repeat for each strata

19
Q

What are the advantages of a stratified sample?

A

Reflects population structure
Guarantees proportional representation

20
Q

What are the disadvantages of stratified sampling?

A

Not always east to classify into distinct strata
Not suitable when strata’s are too large
Sampling frame needed

21
Q

How do you carry out a quota sample?

A

-population divided into groups according to a characteristic
-a quota of people/items in each group is set to try and reflect the groups proportion in the whole population
-interviewer selects actual sampling units

22
Q

What are the advantages of quota sampling?

A

Representative of whole populations
No sampling frame required
Quick/easy/inexpensive
Allows comparison between different groups in population

23
Q

What are the disadvantages of quota sampling?

A

Non random sampling can introduce bias
Population must be divided into groups = costly/inaccurate
Increasing scope of study increased number of groups, adding time/expense
Non responses are not recorded

24
Q

How do you carry out an opportunity sample?

A

Sample taken from people who are available at time of study, who meet criteria

25
Q

What are the advantages of opportunity sampling?

A

East to carry out
Inexpensive

26
Q

What are the disadvantages of quota sampling?

A

Unlikely to provide representative sample
Highly independent on individual researcher

27
Q

What is data with two variables known as?

A

Bivariable data

28
Q

What is the variable on the x axis known as?

A

Independent or explanatory variable

29
Q

What is the variable on the y axis known as?

A

Dependant or response variable

30
Q

What months are measured in the large data set

A

May-October (1987/2015)

31
Q

What is the unit for total sunshine?

A

Hours

32
Q

What is the unit for humidity?

A

%

33
Q

What is the unit for wind speed?

A

Knots

34
Q

What is the unit for cloud cover?

A

Oktas

35
Q

What does trace mean in the large data set?

A

Rainfall < 0.05

36
Q

What are the conditions with a binomial distribution?

A

-there are a fixed number of trials
-there are two possible outcomes
-there is a fixed probability of success
-the trials are independent of each other

A-Level Maths (2 decks)

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