Week 3LSP 120

Joanna Deszcz

2 Methods Particularly if goal is to measure the least

and greatest occurrence of some quantifiable variable

Absolute Quantities Relative Quantities

Measure of the absolute occurrence of the variable

A “sheer” number Tells how many or how much Examples

◦ Number of students enrolled at DePaul◦ Number of people in this class◦ Number of babies born this year

An absolute quantity divided by some other quantity

Calculated value Tells percent, rate, fraction or ratio Examples:

◦ Ticket sales per person◦ Percentage of population infected with HIV by

country◦ Percent increase in population by state

Fraction or Percent◦ Used when comparing part to total of the same

type of variable◦ Percent of people infected with HIV

Infected population/Total population

◦ Also used to show relative change More to come…

Ratio◦ Used to compare the same type of variable from

two sources ◦ Example:

California’s population is 33,872,000 Oregon’s population is 3,421,000 How many times larger is CA than OR? Divide CA/OR = 9.90 CA is almost 10 times larger

Rates◦ Used to compare different types of variables ◦ Examples

Miles per hour Tickets per person Crimes per 1000 people

Let’s work with some absolute and relative quantities

HIV_Adults_By_Country_2001.xls StateLotteries.xls

Describes the actual increase or decrease from a reference (or old/earlier) value to a new (or later) value

Formula◦ Absolute Change = new value – reference value

Compares the absolute change to the reference value

Formula◦ Relative Change = Absolute Change

Reference Valueor

= new value - reference value reference value

◦ Convert relative change from fraction to % (with 2 decimal places) for readability purposes

Absolute and Relative Change

Already discussed◦ Percent Change

Formula = (new-old)/old

◦ Percentage of Main Formula is part/whole=%

◦ Absolute Change Formula = new value – reference(old) value

◦ Relative Change Formula = Absolute Change/Reference Value

Percent More Than or “Times More Than”◦ Example: The life expectancy in Canada is 79.1

years; the life expectancy in the US is 76.0 years.

◦ By how many percent is the life expectancy in Canada higher than the life expectancy in the US? Answer - find percent change (79.1-76.0)/76.0 = 0.041 or 4.1%

◦ How many times as large is the life expectancy in Canada than the life expectancy in the US? Answer – divide Canada LE/US LE 79.1/76.0 = 1.041 times larger

Percent Less Than Same Example: The life expectancy in Canada is

79.1 years; the life expectancy in the US is 76.0 years.

◦ By how many percent is the life expectancy of people in the US lower than the life expectancy in Canada? Answer – find percent change but divide by Canadian

LE (76.0-79.1)/79.1 = -0.039 or -3.9%