Parts of an Experiment

Place these notes into your Class Notebook.

Independent variable – is the variable that is intentionally changed in the experiment, such as the protein in the mouse experiment.There are levels of the independent variable.

Dependent variable – is the variable that responds to the changes in the independent variable. For example, the amount of growth seen in the mice.

Control – is the standard against which the researcher compares the results from each treatment group. In this case the normal level of protein is the control.

Repeated Trials – are the number of times the experiment is repeated to determine how the independent variable affected the results. For example, 100 mice are used for each treatment, so there are 100 trials.

Constants – are the things that are kept the same each time one of the trials in the experiment is repeated. The size and controlled diet of the mice prior to testing.Test one independent variable at a time.As many outside factors as possible should be kept constant in an experiment so the researcher can be sure that any changes that occur do so because of the independent variable.

Experimental DesignTitle:Introduction:Purpose: Explain why is this research important.Hypothesis: Higher protein level in diet will allow mice to grow larger.Background research:Independent Variable (changed variable),(Include Units)• Levels of the (IV) 18% casein, normal protein diet, 9%

casein, low protein diet.e.g. concentration of chemical.

• Number of Trials: Ten or moreDependent Variable (DV)(responding variable) e.g. Group A: 25 grams,

27.5 grams, etc.Group B: 32 grams, 31.3 grams, etc.

Constants: Try to identify at least ten.

Materials list:Procedures: step-by-step instructions for completing and

repeating the experiment.Results: Data Tables and GraphsDiscrete variable results: e.g. dog breeds; makes of cars.

(Use a Bar or Column Graph)

Continuous variable results: e.g. temperature, length, and mass. (Use a Line Graph)

Error: Describe the error mathematically. Percent error works well. (experimental-expected)/expected = percent error

Conclusions: Summarize, and explain cause and effect.

Lab Skills Assessment

Making Tables

Number of animal speciesPhylum Number

Coelenterata 11,000Mollusca 80,000

Arthropoda 826,000Chordata 47,000

Echinodermata 5,000Worms 26,000Porifera 5,000

Making Graphs

Making Graphs

Era Number of years

Number of degrees

Cenozoic 65,000,000 5

Mesozoic 160,000,000 13

Paleozoic 345,000,000 28

Precambrian 3,930,000,000 314

Making Graphs

Making Circular Graphs in Microsoft Excel

Cenozoic

Mesozoic

Paleozoic

Precambrian

a. Eyepieceb. Body tubec. Revolving nosepieced. Low-power objectivee. High-power objectivef. Stageg. Stage clipsh. Basei. Light sourcej. Diaphragm adjustmentk. Arml. Fine focus adjustmentm. Coarse focus adjustment

Laboratory Skills Assessment

How many millimeters wide is the field of view shown? 12.0 mm

Laboratory Skills Assessment

How many millimeters wide is the field of view shown? 12.0 mm

High Power Objective lens = 40XLow Power Objective Lens = 10X

High Power Field of view = Diameter of the Low Power field of view ÷ (HP ÷ LP)

(HP) ÷ (LP) ------ 40X ÷ 10X = 4

2000µ ÷ 4 = 500µ

Organism 1: Approx. 1.3 cm

Field of View: Approx. 3.3 cm

500μ*1.3cm

3.3 cm

Find the width of the organisms by measuring across the organism at several places. Find the central tendency or average width.

1.5 cm 1.4 cm 1.2 cm 1.3 cm 1.1 cm

1.3 cmAverage Width

#4

500µ * 1.3 cm / 3.3 cm = 197µ

500μ * 0.56 cm / 3.3 cm = 84.8μ

500µ * 0.75 cm / 3.3 cm = 113.6μ

The mass indicated on the scale is: 47.52 g

The mass indicated on the scale is:129.07 g

a. 12.5 cm f. 12.0 cm

b. 11.3 cm g. 9.7 cm

c. 13.25 cm h. 12.97 cm

d. 13.95 cm i. 13.34 cm

e. 10.3 cm j. 11.71 cm