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Variables

- Characteristics of observations- May be qualitative/quali (nominal, ordinal) or

quantitative/quanti (interval, ratio)

Primary data

-Secondary data

- from the study of anotherresearcher/organization

Cross-section data

Time series data

- Observations are taken over time

Nominal

- Mere labels / valuesOrdinal

- Values can be ordered from highest tolowest and vice versa

- unknown distance from one value to anotherInterval

- known distance- no natural zero

Ratio

- like interval but there is a natural zeroPopulation

-

Sample

-

Probability sampling

-

Simple random sampling (SRS)

- the usual random drawing of elements- done if population units are assumed or found to

be similar or homogenous with respect to the

variable/s of interest

Systematic sampling

- just like SRS but drawing is for every 2nd, 3rd,4

th, 5

th, etc... element, depending on N/n

- Note: The concept of a Random Start

Stratified sampling

- all groups, some units- done if population units are assumed or found to

be different or heterogenous with respect to the

variable/s of interest

- elements are grouped in such a way that allelements in one particular group are already

similar or homogenous with respect to the

variable/s of interest

- SRS or systematic sampling is then done foreach group or stratum

Cluster sampling- some groups, all or some units- still, an SRS of groups or clusters is done- avoid leaving out a cluster/certain clusters on

purpose

- usually done if researcher cannot reach/accessall possible clusters

Multi-stage sampling

-

Non-probability sampling

-

Judgment sampling

Snowball sampling

Convenience sampling

Quota sampling

Raw data

-

Textual presentation

-

Tabular presentation

-

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Frequency distribution table

- values of qualitative variables as classes- ranges of values of quantitative variables as

classes

o classes should have the same size andshould involve all values in the sample

Class

-

Frequency

-

Relative frequency

- frequency over sample sizePercent frequency

- relative frequency x 100Cumulative frequency

- sum of frequency of class under considerationand those of preceding classes

Cumulative relative frequency

-

Cumulative percent frequency

-

Class limits

- two ends of a classClass boundaries

- usually, lower limit minus 0.5 and upper limitplus 0.5

Class mark

- average of limits or of boundariesBar graph

- qualiPie chart

- quali- usually percentages

Histogram

- quanti

- a bar graph with the bars clustered togetherLine graph

- time series data- trends

Pictogram

Frequency polygon

- class marksOgive

-

Stem-and-leaf display

-

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