Fundamentals of Business Statistics
This domain introduces statistics as a subject: its scope and limitations, collection of primary and secondary data, classification and tabulation, construction of frequency distributions, graphical presentation, and elementary sampling ideas. Questions are often conceptual, but numerical items on class intervals and mid-values are common.
Core rules
- Primary data is collected first-hand (census, survey, experiment); secondary data is already published and must be checked for reliability and comparability.
- Classification groups raw data by attribute or class interval; tabulation arranges it in rows and columns with a clear title, units and source.
- In an exclusive series (10–20, 20–30) the upper limit is excluded; inclusive classes (10–19, 20–29) must be converted by subtracting 0.5 from lower limits and adding 0.5 to upper limits.
- Class width = upper limit − lower limit; mid-value = (lower + upper)/2.
- Less-than and more-than cumulative frequencies are read in opposite directions.
- Histograms suit continuous series; bar charts suit discrete categories; ogives estimate median and quartiles.
Worked example
Convert the inclusive series 10–19, 20–29, 30–39 into exclusive form. Subtract 0.5 from each lower limit and add 0.5 to each upper limit: 9.5–19.5, 19.5–29.5, 29.5–39.5. Each class width is 10 and the mid-values are 14.5, 24.5 and 34.5 - these mid-values are what you substitute as x in grouped mean calculations.
Traps
Leaving class limits in inclusive form, which creates a gap and shifts the mid-value; misreading cumulative frequency totals; and describing a histogram as suitable for discrete data.