"3 out of 4 Americans make up 75% of the population."
 

frequency = number of observations for a particular value; count/tally

proportion = percentage/100

percentage = proportion * 100

relative frequency = proportion of total
 

• higher rates for longer time periods

• event can happen to an individual more than once in a period

• # events could exceed population total

cases = units/elements in a sample

scores = values or observations