Business Mathematics and Statistics · Ch 9 — Collection, Classification and Tabulation of Data
Frequency Distribution — Discrete and Continuous
Frequency Distribution — Discrete and Continuous
A frequency distribution organises quantitative data by listing the values (or groups of values) the variable takes, each against its frequency — the number of times it occurs.
Discrete (ungrouped) frequency distribution. Used for a discrete variable. Each distinct value of the variable is listed with a tally of how many times it occurs. For example, the number of members in 20 families:
| No. of members (x) | Tally | Frequency (f) |
|---|---|---|
| 2 | ||| | 3 |
| 3 | |||| | 5 |
| 4 | |||| || | 7 |
| 5 | ||| | 3 |
| 6 | || | 2 |
| Total | N = 20 |
Continuous (grouped) frequency distribution. Used for a continuous variable, or a discrete variable with a wide range. Values are grouped into class intervals (e.g. 0–10, 10–20, …), each with its frequency. The key terms are:
- Class limits — the two end-values of a class (0 and 10 for the class 0–10): the smaller is the lower limit, the larger the upper limit.
- Class interval / class width (h) — the difference between the upper and lower limits (here 10).
- Class mid-point (mid-value) — the average of the two limits, (lower + upper)/2, used to represent the whole class in later calculations (the average of 0 and 10 is 5).
- Frequency (f) — the number of observations falling in a class. …
The number of times a particular value or class interval occurs …
The difference between the upper and lower limits o …
A class arrangement where the upper limit of one class is the lower limit of the next (0–10, 10–20), with a boundary value placed in the next class …