1. Chapter 3  DESCRIPTIVE STATISTICS: FREQUENCY DISTRIBUTIONS
Understanding Statistics for International Social Work and Other Behavioral Sciences
Serge Lee, Maria C. Silveira Nunes Dinis, Lois Lowe, and Kelly Anders (2015). Oxford University Press

2. FREQUENCY DISTRIBUTIONS
Frequencies. Typically, the term frequency distributions refer to raw scores, percent, valid percent, cumulative percent, and graphs or charts.
Percent or percentile is how people typically calculate percent for the variable.
Valid percent excludes missing data from the calculation.
Notice the denominator. Percent uses n while valid percent depends on valid n.
n = Sample size
Σ = Greek sigma for the sum of the variable
F = Frequency count

3. FREQUENCIES CONTINUED
Cumulative percent is used to indicate position of a particular value. It is helpful to estimate the quartile range for ordinal data when the data set is large.
Cumulative frequency and cumulative percent are helpful in professional practice. For example, 10 out of 200 workers have been with agency X for less then five years. By computation, x 100% = 5%. The result shows that 5% of the workers have been with agency X for less than five years.
Graphs/charts are included within frequency distributions because these figures are always accompanied with numerical scores, percentages, or both.

4. Bar. Nominal data. Bars of graph do not touch each other.
GRAPHS/CHARTS
Four commonly used graphs are bar, pie, histograms, and frequency polygons or line graphs. Use the following criteria to build graph
Bar. Nominal data. Bars of graph do not touch each other.
Pie. Known as crossover. Can be used with any level of measurement but perhaps limit the bars to five or less. Best with nominal data.
Histograms. Interval or ratio data. Bars of graph touch but DO NOT cross each other.
Frequency polygons (line graphs). Similar to histograms. Requires interval or ratio data. Has advantage over histogram graphs due to the fact that several variables can be displayed on the same graph and the lines can crossover each other.

5. DIFFERENTIATE BETWEEN HISTOGRAM AND BAR

6. DIFFERENTIATE BETWEEN FREQUENCY POLYGONS (LINE) AND BAR GRAPH