Identifying%20Variables

1
Identifying Variables
2
Kinds of Variables

• Independent Variable something that is changed
  by the scientist
• What is tested
• What is manipulated
• Changed on purpose to see what may happen

3
Kinds of Variables

• Dependent Variable something that might be
  affected by the change in the independent
  variable
• What is observed
• What is measured
• The data collected during the investigation

4
Kinds of Variables

• Controlled Variable a variable that is not
  changed
• Also called constants
• Allow for a fair test

5
The Bread Experiment

• Lets discuss variables, constants and controls
  using the bread experiment!

6
Problem/Question

• John watches his grandmother bake bread. He asks
  his grandmother what makes the bread rise.
• She explains that yeast releases a gas as it
  feeds on sugar.

7
Problem/Question

• John wonders if the amount of sugar used in the
  recipe will affect the size of the bread loaf?

8
Hypothesis

• The hypothesis is an educated guess about the
  relationship between the independent and
  dependent variables.
• Note These variables will be defined in the next
  few slides.

9
Do you know the difference between the
independent and dependent variables?
10
Independent Variable

• The independent, or manipulated variable, is a
  factor thats intentionally varied by the
  experimenter.
• John is going to use 25g., 50g., 100g., 250g.,
  500g. of sugar in his experiment.

11
Dependent Variable

• The dependent, or responding variable, is the
  factor that may change as a result of changes
  made in the independent variable.
• In this case, it would be the size of the loaf of
  bread.

12
Control Group

• In a scientific experiment, the control is the
  group that serves as the standard of comparison.
• The control group may be a no treatment" or an
  experimenter selected group.

13
Control Group

• The control group is exposed to the same
  conditions as the experimental group, except for
  the variable being tested.
• All experiments should have a control group.

14
Control Group

• Because his grandmother always used 50g. of
  sugar in her recipe, John is going to use that
  amount in his control group.

15
Constants

• John has to keep all other factors the same so
  that any observed changes in the bread can be
  attributed to the variation in the amount of
  sugar.

16
Constants

• The constants in an experiment are all the
  factors that the experimenter attempts to keep
  the same.

17
Can you think of some constants for this
experiment?
18
Constants

• They might include
• Other ingredients to the bread recipe, oven used,
  rise time, brand of ingredients, cooking time,
  type of pan used, air temperature and humidity
  where the bread was rising, oven temperature,
  age of the yeast

19
Another Example
20
Students of different ages were given the same
jigsaw puzzle to put together. They were timed
to see how long it took to finish the puzzle.
21
Identify the variables in this investigation.
22
What was the independent variable?

• Ages of the students
• Different ages were tested by the scientist

23
What was the dependent variable?

• The time it to put the puzzle together
• The time was observed and measured by the
  scientist

24
What was a controlled variable?

• Same puzzle
• All of the participants were tested with the same
  puzzle.
• It would not have been a fair test if some had an
  easy 30 piece puzzle and some had a harder 500
  piece puzzle.

25
Yet Another example
26
An investigation was done with an
electromagnetic system made from a battery and
wire wrapped around a nail. Different sizes of
nails were used. The number of paper clips the
electromagnet could pick up was measured.
27
What are the variables in this investigation?
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Independent variable

• Sizes of nails
• These were changed by the scientist

29
Dependent variable

• Number of paper clips picked up
• The number of paper clips observed and counted
  (measured)

30
Controlled variables

• Battery, wire, type of nail
• None of these items were changed

31
Guess what?One more
32
The higher the temperature of water, the faster
an egg will boil.
33

• Independent variable temperature of water
• Dependent variable time to cook an egg
• Controlled variable type of egg and amount of
  water

34
Last one(I promise)
35
The temperature of water was measured at
different depths of a pond.
36

• Independent variable depth of the water
• Dependent variable temperature
• Controlled variable thermometer and pond

37
Designing Investigations
38
The greater the amount of soap in a soap and
water mixture, the bigger a soap bubble can be
blown.

• Design an investigation to test this hypothesis.
• Identify the variables
• What exactly will be changed? How will it be
  changed?
• What exactly will be measured? How will it be
  measured?

39
Variables

• Independent Variable- soap
• Dependent Variable- size of bubble blown
• Controlled Variable-water and type of soap

• Amount of soap in water mixture
• Size of the bubble blown with different amounts
  of soap in the water

40
The farther a ball drops, the higher it will
bounce.

• Design an investigation to test this hypothesis.
• Identify the variables
• What exactly will be changed? How will it be
  changed?
• What exactly will be measured? How will it be
  measured?

41
Variables

• Independent Variable- length of fall
• Dependent Variable-height of bounce
• Controlled Variable- ball, surface, size of the
  ball

• The length of the fall, different fall for each
  trial
• The height of the bounce from the different
  lengths of the fall the higher the height of
  the fall the higher the bounce