N OTES V ARIABLES

V ARIABLE A factor in an experiment that changes or could be changed There are 3 types

I NDEPENDENT V ARIABLE Variable that is changed on purpose, it is what you are testing. You manipulate it to see how it affects the dependent variable. There can only be one (1) independent variable in any investigation or experiment.

D EPENDENT V ARIABLE The variable that responds to changes in independent variable, it is what you look for changes in. This is the factor that you measure in an experiment. This is the observed result of independent variable changes. There can be more than one in an experiment

C ONTROL Often called control group This is what you compare your results to. Not manipulated or changed in any way. Example: Investigating how a weight affects the length of an elastic band. Use the same elastic band each time Use the same scale each time

C ONSTANTS Sometimes mistaken for control This is what you compare your results to. These are factors you need to manage so they don’t change your results. Usually small things that would not seem to matter. Example: The way you held the dropper in the penny lab, the way you released the helicopter, the height you dropped it from.

P RACTICE Identify variables for the following experiments.

P RACTICE QUESTION 1 Does changing the temperature of a ball affect the height the ball will bounce?

P RACTICE QUESTION 1 Does changing the temperature of a ball affect the height the ball will bounce? Written in the blue is the dependant variable Written in red is the independent variable Control variables on next slide

C ONSTANTS Same ball Dropped from same height Dropped onto same surface Control Dropping the ball at normal temp.

P RACTICE QUESTION 2 Does changing the color of light affect the growth rate of plants?

P RACTICE QUESTION 2 Does changing the color of light affect the growth rate of plants? Written in the blue is the dependant variable Written in red is the independent variable Control variables on next slide

C ONSTANTS Same type and size of plant Same wattage of bulb Same amount of water Same soil Light on for same amount of time Etc…

V ALID E XPERIMENT Everything you have seen goes into making an experiment VALID. Can be repeated by anyone & get same or similar results. It should also have a good control group with a good comparison. Well monitored variables Good written procedure

N OTES G RAPHS

T YPES OF GRAPHS A graph is just a picture of an amount of something. Like size of buildings since 1900.

Circle or pie graph. Shows fractions of a whole.

Bar graph uses bars to show the data (words or numbers).

Histogram used to show pure numbers in order. Range of data can be shown, bars should be touching.

Line graph, shows points plotted on a graph connected by a line. Any type of data.

On a typical graph there are 2 axis. an X and a Y.

Your independent variable goes on X axis ( it is almost always time) Your dependent variable goes on Y axis

Your X and Y axis scale can be different but the spacing between the numbers should be the same on an axis. Graphs should have title, and descriptions on both X and Y axis.

In other words your graph should TALK T title descriptive A axis evenly spaced L label both axis and title K key or legend if needed

V OCABULARY Two very important terms when working with graphs. Interpolation and Extrapolation

Interpolation – is when you find a value that lies on the smooth curve or line between two actual data points.

Extrapolation – Find a value that lies on the smooth curve or line beyond the actual plotted points.