Descriptive statistics is a process of concisely summarising the characteristics of sets of data.
Inferential statistics involves constructing estimates of these characteristics, and testing hypotheses
about the world, based on sets of data.
Modelling and analysis combines these to build models that represent relationships and trends in
reality in a systematic way.
Types of Data:
Numerical or quantitative data are real numbers with specific numerical values.
Nominal or qualitative data are non-numerical data sorted into categories on the basis of qualitative
Ordinal or ranked data are nominal data that can be ranked.
- The population is the complete set of data that we seek to obtain information about
- The sample is a part of the population that is selected (or sampled) in some way using a
- A characteristic of a population is call a parameter
- A characteristic of a sample is called a statistic
- The difference between our estimate and the true (usually unknown) parameter is the
- In a random sample, all population members have an equal chance of being sampled
In a population, a perfect strata would be a group with:
- individual observations that are similar to the other observations in that strata
- different characteristics from other strata in the population
- stratified sampling can improve accuracy
- may be more costly
In a population, a perfect cluster would be a group with:
- individual observations that are different from the other observations in that cluster
- similar characteristics to other clusters in the population
- can reduce costs
- may be less accurate
This is the cost/accuracy trade off
Ceteris paribus: the assumption of holding all other variables constant
Cross-sectional data are:
- collected from (across) a number of different entities (such as individuals, households, firms,
regions or countries) at a particular point in time
- usually a random sample (but not always)
- not able to be arranged in any “natural” order (we can sort or rank the data into any order
- often (but not only) usefully presented with histograms
Time series data are:
- collected over time on one particular ‘entity’
- data with observations which are likely to depend on what has happened in the past
[ECON10005: QUANTITATIVE METHODS 1:
LECTURE REVISION NOTES]