Trendlines & Excel

Same Log In

• Press: Control-Alt-Delete

• Username: physics

• Password: success

Same Example Experiment

How big will your goldfish be if you fed it 7.5 pellets per day?

?

Use Your Old Data

food (pellets/day) mass (g)

1 6

2 8

3 13

4 15

5 25

6 34

7 52

8 78

9 94

10 121

After 6 months…

Do Over: Enter Your Data

• Row 1: Names

• Row 2: Date

• Row 3: Blank

• Row 4: Headings

• Row… : Data

Graph It Again

Goldfish Growth

0

20

40

60

80

100

120

140

0 2 4 6 8 10 12

Food (pellets/day)

Mas

s (g

)

Ingredients:

• Meaningful Title

• Labeled Axis

• Units in Parentheses

• White Background

• No Gridlines

Mathematical Relationships(Trend Lines)

Have Excel draw lines through your data.

Pick the “best fit” line.

Excel gives you the equation.

Use the equation to make a prediction.

Ex: Calculate the goldfish’s mass if it is fed 7.5 food pellets per day.

Example: Add a “Best Fit” Trend Line to our Goldfish Growth Graph

Goldfish Graph

Next: You add a best fit trend line

to the examples.

Linear Relationship

• Use a straight line.

• Mathematically:

• The dependent variable (y) does the same thing as your independent variable (x).

bmxy

Inverse Relationship

• Excel calls this a Power function

• Mathematically:

• exponent = -1 ← makes this an inverse

• Your dependent variable (y) does the opposite of your independent variable (x)

1axx

ay

Quadratic Relationship

• Excel calls this a Polynomial function• Order = 2 ← this makes it a quadratic

• Mathematically: cbxaxy 2

Notes:

Your Turn

Enter your data for the heights and stopping distances you measured yesterday.

Your Turn

Find the best fit trend line. Use the equation to predict how far it would take your cart to stop if released from 65 cm.

Print & Save

Save on your floppy diskor it will be lost forever.