Scientific Method

Steps in the Scientific Method Problem / Question Observation Hypothesis Experiment Data Collection Conclusion Retest

Solving a Problem 1)Identify a Problem 2) State Observations about the problem 3) Form a Hypothesis about the problem (if…then…) 4) Design an Experiment to test the hypothesis 5) Collect Data 6) Form a Conclusion 7) Retest

Observations Gathered through your senses A scientist notices something in their natural world

Observations An example of an observation might be noticing that many salamanders near a pond have curved, not straight, tails

Hypothesis A suggested solution to the problem. Must be testable Sometimes written as If…Then… statements Predicts an outcome

Hypothesis An example of a hypothesis might be that the salamanders have curved tails due to a pollutant in the moist soil where they live.

A procedure to test the hypothesis. Experiment A procedure to test the hypothesis.

Variable – factor in the experiment that is being tested

A good or “valid” experiment will only have ONE variable!

Scientific Experiments Follow Rules An experimenter changes one factor and observes or measures what happens.

The Control The experimenter makes a special effort to keep other factors constant so that they will not effect the outcome. Those factors are called constants / controlled variables.

What is the Purpose of a Control? Controls are NOT being tested (they remain the same/normal ) Controls are “standards” used for COMPARISON

Other Variables The factor that is changed is known as the independent variable. The factor that is measured or observed is called the dependent variable.

Example of Constants & Variables For example, suppose you want to figure out the fastest route to walk home from school. You will try several different routes and time how long it takes you to get home by each one. Since you are only interested in finding a route that is fastest for you, you will do the walking yourself.

What are the Variables in Your Experiment? Varying the route is the independent variable The time it takes is the dependent variable Keeping the same walker throughout makes the walker a constant / control variable.

One more thing… it is best to make several trials with each independent variable.

Remember: To be a Valid Experiment: Two groups are required --- the control & experimental groups There should be only one variable

Data Results of the experiment May be quantitative (numbers) or qualitative Precision / accuracy

Step 5 - graphs, data tables, ratios, frequency/ percentages, or totals Examples: * Blonde Hair Brown Hair Red Hair Black Hair 1st 4 6 1 3 2nd 3 9 7 3rd 1 5 2 4 * 3 of 6 kittens are white = 3/6 = 1/2 = 50% * 30 m&m’s in bag, 10 are brown > 3:1 ratio

Step 5 – Data is always measured in metric units S.I. – International System of Units length – km, m, cm, mm mass – kg, g, mg volume - L, mL, cc or cm3 temperature - oC or oK time - seconds, minutes, hours, days, years…

Data Must be organized Can be organized into charts, tables, or graphs

•Graphs help us visualize numerical data. Why Do We Use Graphs? •Graphs help us visualize numerical data. •There are several different types of graphs: –Bar graphs –Pie graphs –Line graphs

Bar graphs are used to show a comparison of multiple objects •

Pie graphs are used to compare the parts of a whole •

Line Graphs Line graphs are used to show the relationship between variables.

Conclusion The answer to the hypothesis based on the data obtained from the experiment

In order to verify the results, experiments must be retested. -Results that are the best explanation for validated data may become a theory.

Step 6 – Conclusions – (may or may not prove your hypothesis.) Theory –best tested explanation of natural events; however, cannot be ‘proven’ Law - tested and proven to be factual time after time

Solving a Problem 1)Identify a Problem 2) State Observations about the problem 3) Form a Hypothesis about the problem (if…then…) 4) Design an Experiment to test the hypothesis 5) Collect Data 6) Form a Conclusion 7) Retest

Review

Controls and Variables

Valid Experiments