U1 - collecting data Flashcards
quantitative data definition
numerical data (numerical observations or measurements)
qualitative data definition
non-numerical data (non-numerical observations)
continuous data definition with examples
how can this data be represented?
can take any value on a continuous numerical scale. grouped data with inequalities.
e. g.
- height
- weight
- temperature
- length
can be represented by:
- histograms
- cumulative frequency curves
- line graphs
discrete data definition with examples
how can this data be represented?
can only take particular values. grouped data with no inequalities
e. g.
- the number of students in a class
- shoe size
- the number of languages an individual speaks
can be represented by:
- bar charts
- CF step polygons
categorical data definition with examples
how can this data be represented?
can be sorted into non-overlapping categories.
e. g.
- race
- sex
- age group
can be represented by:
- frequency tables (normal freq tables, relative freq tables, cf tables)
- pie charts
- bar charts
ordinal data definition with examples
how can this data be represented?
like categorical data but can be written in order and given a rating scale
e. g.
- spicy scale (plain, mild, medium, hot, extra hot)
- income level (low income, medium income, high income)
- satisfaction level (extremely dislike, dislike, neutral, like, extremely like)
can be represented by:
- bar charts
- pie charts
- tables
bivariate data definition with examples
how can this data be represented?
involves a pair of related data, helps you study correlation between two variables
e. g.
- how temperature affects the state of an ice cream (two variables are temperature and ice cream)
can be represented by:
- scatterplots
multivariate data definition with examples
how can this data be represented?
involves sets of 3 or more related data values. involves multiple dependent variables that result in one outcome
e. g.
- predicting the weather (multiple factors like pollution, humidity, precipitation, etc)
can be represented by:
- radar charts
population definition
everything or everybody that could possibly be involved in an investigation
census definition
a survey of a whole population
sample definition
a smaller number of items from the population
biased sample definition
not representative of everyone in the population
sampling frame definition
a list of people/items that are to be sampled
advantages of primary data (3)
- accurate
- collection method is known (because its your own)
- you can find answers to specific questions
disadvantages of primary data (2)
- time consuming
- usually expensive
advantages of secondary data (4)
- cheap
- easy
- quick
- data from some organisations can be more reliable than data collected yourself
disadvantages of secondary data (5)
- method of collection is unknown
- data may be out of date
- may contain mistakes
- may come from an unreliable source
- may be difficult to find answers to specific questions
advantages of a census (3)
- unbiased
- accurate
- takes the entire population into account
disadvantages of a census (4)
- time consuming
- expensive
- lots of data to manage
- difficult to ensure the whole population is used - if some are missed, the survey may be biased
advantages of a sample (3)
- cheaper
- quicker
- less data to consider
- easier to get hold of all the required information
disadvantages of a sample (2)
- may be biased
- not representative of the entire population - each possible sample will give different results, so the one selected might not accurately reflect the population
impact of a sample size on reliability and replication
the bigger the sample size, the better the estimate of the population parameters
what is the peterson capture-recapture method
a way of estimating the size of a population, usually dealing with wildlife.
peterson capture-recapture: population size formula
population size = (number in 1st sample x number in 2nd sample) / number in 2nd sample that are marked
