Statistics 1: Intro To Stats

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Statistics

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Science of collecting organising analysing and interpreting data to draw relevant conclusions

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Variable

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Characteristics or attributes that can take different values

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Subgroup

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Sample of subset of the population

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Data

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Set of values of qualitative or quantitative variables

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What is categorical data?

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Qualitative data define a category or a group

nominal: two or more categories but do not have order for example blood type for gender

Ordinal: two or more categories but can be ordered or ranked however distance between is not defined for example socioeconomic status and grades

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What is numerical data?

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Quantitive data represents and measurement.

Discreet: has a countable number for example number of children in a family.

continuous: can take any value in any range of values from sample height weight volume.

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What is primary and secondary data?

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Primary data collected and used for the first time by the researcher

secondary data already collected and produced by others and need to be obtained by published sources

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What are is census and sample?

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Census collection of data from whole population

Sample collection of data from part of population

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What is Sample variation?

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Sample variation takes into account when using a sample that different sample from the population will give different results due to chance.

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What are two main categories of sampling methods?

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Probability / random: all subjects in population have equal chance of being selected in sample

Non-probability / random:sample selected in non systematic process that does not guarantee equal chance.

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What are probability sampling methods?

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Simple random sampling: whole populations must be accessible.

Stratified Sampling: reduces sampling error that whole population must be accessible. Identify strata which is a subset of population that has at least one common characteristic and then using random sampling to select sufficient numbers of subjects form each stratum.

Only used when one or more strata has a low incident rate compared to another.

Simple and stratified sampling is more reliable than quota.

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What are non-probability sampling methods?

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Judgement sampling: research essay example based on judgement.

Quota sampling: similar to stratified sampling stratas are identified then judgement sampling is used to select require numbers from in Stratum. Number collected is predefined quota.

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What is unbiased and precise measurements?

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Unbiased measurements is when the mean of data set it was close to true value.

Precise measurement is when repeated measurements are close to one and another.

Larger sample size = more unbiased and precise measurements.