Economics · Ch 3 — Organisation of Data
Conclusion
3.7
Conclusion
Data from primary and secondary sources arrive raw and unclassified, so the step after collection is to classify them for analysis — because classification brings order to what is otherwise unmanageable.
Note
Recap
- Classification brings order to raw data.
- A Frequency Distribution shows how the different values of a variable are distributed in different classes along with their corresponding class frequencies.
- Either the upper class limit or the lower class limit is excluded in the Exclusive Method.
- Both the upper and the lower class limits are included in the Inclusive Method.
- In a Frequency Distribution, further statistical calculations are based only on the class mark values, instead of values of the observations.
- The classes should be formed in such a way that the class mark of each class comes as close as possible, to a value around which the observations in a class tend to concentrate.
The main threads of the chapter:
- Classification arranges raw data into groups on some criterion, saving effort and revealing structure.
- A frequency distribution shows how the values of a variable spread across classes, each with its frequency.
- In the exclusive method one limit (upper or lower) is excluded from a class; in the inclusive method both limits are included, with an adjustment to restore continuity.
- After grouping, calculations rest only on class marks, not on the original observations (the accepted loss of information).
- Classes should be formed so each class mark lies as close as possible to where its observations concentrate — the reason unequal intervals are sometimes preferred.
- Continuous data use class intervals; discrete data use a frequency array; two variables together are shown in a bivariate frequency distribution.
With these techniques you can construct a frequency distribution for both continuous and discrete variables.
Think About It
Suggested Activity
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