Sampling Flashcards

1
Q

What does it mean if data is qualitative?

A

When data can be in categories eg flavour of cupcakes of place of birth

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2
Q

What does it mean if data is discrete?

A

The data can only take individual distinct values eg number of siblings or shoe size

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3
Q

What does it mean if data is continuous?

A

Something that can be measured and recorded to any accuracy eg height or weight

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4
Q

What is a population in sampling?

A

All the possible values a variable can take eg heights of all adult females

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5
Q

When are samples used?

A

If It is impossible or not advisable to investigate the whole population, usually as it would be impractical or destructive
Eg
You can’t interview everyone in the uk
And to test the lifespan of an entire population of lightbulbs would destroy all the lightbulbs

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6
Q

Why does the sample need to be as representative of the population as possible?

A

The sample will be used to draw conclusions about the population

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7
Q

What is a parameter?

A

A statistical measure of the entire population eg standard deviation or mean height of all women in uk

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8
Q

What is a statistic?

A

A statistical measure carried out on a sample eg mean height of a sample of women in the uk

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9
Q

Population => Parameter
Sample => Statistic

A
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10
Q

Define a truly random sample

A

A random sample of size n is a sample selected in such a way that all possible samples of size n have an equal chance of being selected

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11
Q

What is a simple random sample?

A

A random sample that does not allow any repetition (without replacement)

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12
Q

In simple random sampling how are numbers picked?

A

Random number generator

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13
Q

Give some advantages and disadvantages of simple random sampling

A

Advantages
Most statistical methods assume a random sample
Only method which is truly random
Disadvantages
Can be very time consuming
With large target population can be impossible to carry out
List of whole population needed

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14
Q

What is opportunity sampling?

A

Taking the sample from people who are available at the time the study is being carried out and fit the criteria you are looking for
Eg you use the first 20 people who enter the dining room

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15
Q

What are some advantages and disadvantages of opportunity sampling?

A

Advantages
May save time and money
Can be seen as adequate when investigating processes which are thought to work in similar ways for most individuals such as memory processes.

Disadvantages
Likely to produce a sample not representative of the population
Researcher may choose people from their own social and cultural group
Some people may refuse to take part making the sample self selecting

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16
Q

What is stratified sampling

A

Population is divided into relevant strata and random samples are taken from each strata in proportion to the size of the strata
From each strata a random sample will be taken

17
Q

What are some advantages and disadvantages of stratified sampling

A

Advantages
More representative of the population than a simple random sample
Disadvantages
Prior knowledge needed to divide population into relevant strata
Could be time consuming and expensive

18
Q

What is quota sampling

A

A stratified sample where the samples from each strata are chosen in the most convenient way

19
Q

What are some advantages and disadvantages of quota sampling

A

Advantages
Cheap n straightforward
Can be used when population list not available
Disadvantages
Prior knowledge needed to divide population into relevant strata
Some people may refuse to take part
Bias due to investigators preference
May be hard to tell if people are part of relevant quota or not

20
Q

What is systematic sampling?

A

Members of population are chosen at regular intervals

21
Q

What are some advantages and disadvantages of systematic sampling

A

Advantages
May be very easy to administer
Disadvantages
List of population needed
Some members of population may not have an equal chance of being choses

22
Q

What is a cluster sample

A

A cluster is a pre existing grouping in the population a cluster sample will study randomly chosen clusters of the population
Eg study only schools in Leicestershire

23
Q

Advantages and disadvantages of cluster sampling

A

Advantages
Members of cluster May be geographically close saving time and money
Disadvantages
A cluster of samples may not be representative of the population. For example a post code may contain certain types of residents

24
Q

When is a stratified sample better than a random sample?

A

If relevant prior knowledge available as sample more likely to be representative of the population whilst still including some randomness

25
Q

Quota cluster and systematic samples are used to overcome the practical problems associated with random sampling but a random sampling is usually preferred to these methods

A