GraphingGraphing““The basics”The basics”

The BasicsThe BasicsGraphs give us a way to Graphs give us a way to picture data. picture data.

Basically, graphs provide Basically, graphs provide a picture of a data table. a picture of a data table.

So, what is data? What is So, what is data? What is a data table?a data table?

DataDataLet’s first talk about Let’s first talk about datadata. .

Data is simply information. This Data is simply information. This information can be about anything… information can be about anything… from the height of a person to how from the height of a person to how much rain fell in a year. much rain fell in a year.

The key to looking at this data, is to The key to looking at this data, is to organize it…organize it…

Data TableData TableWhen we make observations and list our When we make observations and list our data, we often put the information in a data data, we often put the information in a data table. table.

A A data tabledata table is a way of organizing data in is a way of organizing data in columns so it is neat and readable.columns so it is neat and readable.

100100 200200 300300 400400 500500

2.12.1 4.54.5 3.43.4 1.61.6 3.73.7

Data TableData Table

Data tables begin with a Data tables begin with a titletitle which describes the which describes the content.content.

Data tables also include variables and units…Data tables also include variables and units…

Student Shoe SizeStudent Shoe Size

Number of Number of StudentsStudents

44 99 77 22 11

Shoe SizeShoe Size 5 1/25 1/2 66 6 1/26 1/2 77 7 1/27 1/2

VariablesVariables

Variables describe Variables describe what information is what information is recorded.recorded.

For example time For example time would be a variable, would be a variable, can you think of can you think of other variables?other variables?

UnitsUnits

Units tell how the variable Units tell how the variable is measuredis measured

If we used time as a If we used time as a variable, our units could variable, our units could be hours. be hours.

Can you think of other Can you think of other units we use for time?units we use for time?

Ordered PairsOrdered Pairs

Finally, the information in a data table is Finally, the information in a data table is organized with ordered pairs.organized with ordered pairs.

Ordered pairs are two pieces of data Ordered pairs are two pieces of data directly corresponding to one another.directly corresponding to one another.

High Temperature During the High Temperature During the WeekendWeekend

DayDay SaturdaySaturday SundaySunday

TemperatureTemperature 7575°° 7878°°

We might We might have a have a temperature temperature of 72of 72°C at a °C at a time of 30 time of 30 seconds. seconds.

Our ordered Our ordered pair would be pair would be 72°C and 30 72°C and 30 seconds.seconds.

Time Time (seconds)(seconds) 2525 3030 3535

Temp (Temp (°C)°C) 7070 7272 7474

For instance, if we are measuring a change For instance, if we are measuring a change in temperature over a period of time…in temperature over a period of time…

Types of VariablesTypes of Variables Ordered pairs consist of Ordered pairs consist of

independent and independent and dependent variables.dependent variables.

The independent variable The independent variable “stands alone” and the “stands alone” and the dependent variable dependent variable “relies” on the changes in “relies” on the changes in the independent variable.the independent variable.

For example, let’s think about the For example, let’s think about the change in temperaturechange in temperature throughout throughout

the year…the year…

So, what is the So, what is the independent variableindependent variable in in this example?this example?

What is the What is the dependent variabledependent variable in this in this example?example?

Which variable relies on the other? Which Which variable relies on the other? Which variable stands alone?variable stands alone?

Independent or Dependent??Independent or Dependent??

Let’s think about this… does time Let’s think about this… does time change because of the change because of the temperature?temperature?

No… time doesn’t change because No… time doesn’t change because of temperature… it stands alone. of temperature… it stands alone.

Therefore, Therefore, timetime is the independent is the independent variable!!variable!!

What about Temperature??What about Temperature?? Does the change in temperature depend Does the change in temperature depend

on what time of year it is?on what time of year it is?

YES!! So, temperature is the dependent YES!! So, temperature is the dependent

variable. variable.

It relies on changes in the independent It relies on changes in the independent variable “time”.variable “time”.

Dependent Variables…Dependent Variables…

REMEMBER!!REMEMBER!!

The Dependent The Dependent variable always variable always reliesrelies on changes on changes in the independent in the independent variable!!!variable!!!

Tomorrow…Tomorrow…

Next we will Next we will use this use this information to information to understand understand graphs!!!graphs!!!

TypesTypes

We are going to We are going to talk about…talk about…

Line GraphsLine Graphs

Bar GraphsBar Graphs

Pie GraphsPie Graphs