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DATA, SAMPLING AND VARIATION IN DATA AND SAMPLING

Qualitative Data

Data

Sampling

Variation in Data

The result of categorizing or describing attributes of a population.

Quantitative discrete data

Quantitative continuos data

All data that are result of counting. It take on only certain numerical values

All data that are result of measuring.

The result o f counting or measuring atributes of a population. Are always numbers.

Quantitative Data

Discussion

Pie Chart; categories of data are represented by wedges in a circle and are proportional in size to the percent.

Bar graph; the length of the bar for each category is proportional to the or percent of individuals

Pareto chart; bars that are sorted into order by category size.

Random Sampling

Simple random sample

Any group of n individuals is equally likely to be chosen by any other group of n individuals

Stratified sample

Divide the population into groups called strata and then take a proportionate number from each stratum.

Cluster sample

Divide the population into clusters (groups) and then randomly select some of the clusters, all the members from these clusters are in the cluster sample.

Systematic sample

Randomly select a starting point and take every n th piece of data from a listing of the population.

With replacement

Without replacement

Once a member is picked, that member goes back into the population and thus may be chosen more than once.

A member of the population may be chosen only once.

Is present in any set of data

Convenience sampling

Involves using results that are readily available

Two or more samples from the same population, taken randomly, and having close to the same characteristics of the population will likely be different from each other