Some Formulas – Proportions, Percentages, Counts

The class represents some property or attribute, for example, blue, or red. Each member, or unit, of a sample can be classified – the result of the classification of the unit is the unit’s class.

Sample Proportion (p)

p_class = n_class / n_total

p_class ~ proportion of sample in class

n_class ~ number of units of sample in class

n_total ~ total number of units in sample

Sample Percent (pct)

pct_class = 100*(n_class / n_total)

pct_class = 100* p_class

pct_class ~ percent of sample in class

n_class ~ number of units of sample in class

n_total ~ total number of units in sample

Population Proportion (P)

P_class = N_class / N_total

P_class ~ proportion of population in class

N_class ~ number of units of population in class

N_total ~ total number of units in population

Population Percent (PCT)

PCT_class = 100*(N_class / N_total)

PCT_class = 100* P_class

PCT_class ~ percent of population in class

N_class ~ number of units of population in class

N_total ~ total number of units in population

Perfect (Expected) Count (e)

e_class = n_total * P_class

e_class ~ expected or perfect count of class in a sample of n_total units

P_class ~ proportion of population in class

n_total ~ total number of units in sample