10/4/20151 Graphs

2 Today we are going to graph. What are the parts of a graph?

3 The parts of a Graph Axes- one line going across the bottom & another up the side Horizontal axis (horizon): goes along the bottom Vertical axis: goes up the left side of the page

4 YOU TELL ME…. What color is the y-axis? What color is the x-axis? Y X

5 The parts of a Graph Identifying the Lines  Independent: This is what you measure with regularity. –It is predictable (measuring time every minute, increasing weight by 10 grams) Independent (units) Dependent (units)  Dependent: This is what you are measuring. –It changes; it is unpredictable; it is what you want to know about the experiment (how does the temp. change, how does speed increase, how does Force change)

10/4/20156 The parts of a Graph Units: How do you measure the independent & dependent variables? - Meters ( m), seconds (s), millimeters (mm), minutes (min), Force (N)  Without units, you don’t know how the distance or time was measured, and the data is worthless to you time (s) Distance (m)

7 Scale When we are setting up a line graph, we need to decide what scale we want to use. If we are graphing the distance traveled for 400 s, do we want to put 400 s on the graph, and 100 different distances? time (s) Distance (m) The x and y-axis usually starts with zero on a line graph The parts of a Graph

8 Title: The finishing touch –Tells us what all these numbers and lines mean –Don’t be too clever or fancy –It is usually named y vs x (dependent vs. independent) time (seconds) Distance (m) Distance vs time

10/4/20159 Collecting Data Make a chart of x and y: and fill in the information time (seconds) (X) Distance (m) (Y) Last But Not Least…

10 Make your own….. Now that you have learned the parts of a graph, you will be making your own graph. You will graph distance vs time. Use the data given to you to do this.

Distance vs. Time 10/4/201511

10/4/ Distance vs. Time

Linear Relationship A linear relationship is a relationship between the x & y variable where the x & y variable are directly proportional (direct variation). As x increases, y increases proportionally. The graph of a linear relationship is a straight line and is represented by the equation y = mx +b.

Slope Slope is calculated using the formula to the right. ALWAYS select 2 points on the line AS FAR APART AS POSSIBLE. The y-intercept (b) is the point where the line crosses the y-axis when x is zero.

10/4/ When constructing a graph, you must draw a line that best represents ALL of your data. The Line of best fit is a line that best passes through or near graphed data. It is used to describe data and predict where new data will appear on the graph. Line of Best Fit

Distance vs. Time: Distance vs. Time: Not always perfect! 10/4/ On each graph, the data points are scattered and do not always make a straight line. The line of best fit is used to best represent all the data – usually in the “middle” of all the data.

Distance vs. Time: 10/4/ NO MORE CONNECT-THE-DOT GAME!!! CONNECTING DATA POINTS IS NOT ALLOWED!!! When making a line on a graph, you will NO LONGER connect the dots – you will make a LINE OF BEST FIT, as we discussed earlier… CONNECTING DATA POINTS IS NOT ALLOWED!!!

10/4/ Types of Graphs Bar Graph Line Graph

10/4/ Line Graph A line graph is a graph used to show change over time !! What can time be measured in??? Seconds - Minutes - Hours – Days - Weeks - Months – Years - Decades - Centuries - etc.

10/4/ When to use a line graph? Would we use a line graph in the following situations: To show how many people like pizza in this class? NO To show how many people live in Edison? NO To show how much it rained each month this year? YES- because months and years deal with time.

10/4/ Birthdays? Our birthday does deal with time doesn’t it? (months/years) But, our birthday is constant, meaning it never changes. A line graph shows change in time, so we would not use it for this type of graph. Would we use a line graph to show when our birthdays are?

10/4/ Practice With Graphs Please study the graphs that you have and answer the questions. Then we will discuss the your answers.

10/4/201523

10/4/ Q & A Which day did this person spend the most money? How do you know? This person spent the most money on Wednesday. I know this because the graph is the highest on Wednesday. About how much money in total did this person spend on Monday and Thursday? How do you know? This person spent about $9.00 on Monday and Thursday. I know this because I looked at where the line was for Monday and Thursday and added the two amounts.

10/4/201525

10/4/ Q & A How many days did this person travel less than 30 miles? Which day did the driver travel the least amount of miles? Why might someone want to keep track of their miles for the week? 5 days Sunday To figure out how much gas they need a week.

10/4/201527

10/4/ Q & A About how much corn did the U.S. have in 1991? What does the y-axis represent in the graph? Can you think of another title for this graph? About 77 million acres The rise and fall of corn in the U.S. Acres of corn in millions.

10/4/201529

10/4/201530

10/4/201531

10/4/201532

10/4/ Do these have the same information on them?

10/4/ Great Job!