The Scientific Method in Action

SCIENCE If you don’t make mistakes, you’re doing it wrong If you don’t correct those mistakes, you’re doing it really wrong If you can’t admit that you’re mistaken – then you’re not doing it at all!

What is Science? (verb) it is an activity carried out by scientists, with certain raw materials, purpose and methodology in order to gain knowledge (noun) it is the result of this activity: a well-established and well-tested body of facts, laws and models that describe the natural world.

Science involves the critical evaluation of ideas and information Scientists maintain a “healthy skepticism” about information and ideas the best way to evaluate ideas is the scientific method Only field where ideas are tested

Where do we get knowledge? Acceptance of “truth” From inherited customs, traditions Authority figure Trial and error Deductive reasoning Assumptions from existing knowledge Uses logical arguments (If… then)

In God We Trust – all others must have data

Scientific Method Scientific knowledge begins with an observation and a proposed explanation. Explanation called a hypothesis A hypothesis is testable and falsifiable In science hypotheses are tested by using them to make predictions about the outcome of an experiment

(a) Describe how scientific method involves interplay between observations and the formation, testing and evaluation of hypotheses. The principle of scientific method is based on the collection of data by observation and experimentation and the formulation of hypotheses. The hypotheses may be subsequently refined on the basis of the observations. Scientific research involves proposing hypotheses to explain observed phenomena, then designing and carrying out experiments to test the hypotheses.

Scientific Method Scientific method More reliable for obtaining information You can test what you believe to be true Others can repeat your experiment Opportunity to prove false Follows general set of systematic procedures Steps are followed in order to answer a research question

Ethics

The Scientific Method Observe an event. Develop a Hypothesis which makes a prediction. Test the prediction. Observe the result. Revise the hypothesis. Repeat as needed. A successful hypothesis becomes a Scientific Theory. hypothesis test

Scientific Method Everyday Science Observation Spaghetti sauce is red. Hypothesis (prediction) Use tomatoes. Test Heat pot of tomato sauce. Observe result Taste the sauce - bland. Revise hypothesis? Use tomato sauce and garlic! New test? Add garlic, taste - not so bland. Scientific Theory Grandma’s Recipe.

Scientific Method Medical Science Observation Patient has high cholesterol Hypothesis (prediction) Certain chemicals may dissolve cholesterol deposits. Test Give 100 patients these chemicals, give 100 patients placebo. Observe result Same number lower their cholesterol as placebo patients. Revise hypothesis? Try different combo of chemicals. New test? Re-run medical test. Observe results. Scientific Theory Lipitor reduces cholesterol.

How many variables do you test at one time?

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

Caution! Be careful how you use effect and affect. Effect is usually a noun and affect, a verb. “ The effect of sugar amounts on the rising of bread.” “How does sugar affect the rising of bread?”

Observation/Research John researches the areas of baking and fermentation and tries to come up with a way to test his question. He keeps all of his information on this topic in a journal.

Formulate a Hypothesis After conducting further research, he comes up with a hypothesis. “If more sugar is added, then the bread will rise higher.”

(b) Design experiments to test a given hypothesis, in which variables are controlled and quantitative results are collected. Candidates should be able to apply their knowledge of practical techniques to design experiments. As an example, to design an experiment to test the hypothesis that the rate of photosynthesis of an aquatic plant increases as light intensity increases. In this example, it is important to recognize that light intensity is the key variable and others, including temperature and the wavelength of light are the control variables. The effect of control variables should be eliminated by careful experimental design if valid results are to be obtained. The nature of the results obtained depends on the actual investigation, but could include measurements of volume, time, length, mass or temperature, with appropriate SI units. If a rate is measured, this should be expressed in relation to time.

Ockams Razor It states that among competing hypotheses, the one with the fewest assumptions should be selected. Other, more complicated solutions may ultimately prove correct, but—in the absence of certainty—the fewer assumptions that are made, the better.

(d) Formulate a hypothesis on the basis of experimental data. With reference to experimental data, candidates should be able to state an operational hypothesis. For example, a table of data might suggest that, as the concentration of nitrate ions increases, the growth of algae also increases. From the data, candidates could suggest the hypothesis that ‘there is a positive relationship between the concentration of nitrate ions and the growth of algae’.

Note: These variables will be defined in the next few slides. 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.

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

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

In this case, it would be the size of the loaf of bread. 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.

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.

All experiments should have a 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.

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

Independent variable: condition or event under study (only 1 can reliably be tested at one time) Dependent variable: condition that could change under the influence of the independent variable (what you measure) Controlled variables: conditions which could effect the outcome of the experiment so they must be held constant between groups This is especially important as your results have little significance without a controlled experiment. Remember, “correlation does not equal causation” Used for comparison

Causation vs Correlation

Constants John’s teacher reminds him 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.

Constants The constants in an experiment are all the factors that the experimenter attempts to keep the same. Can you think of some constants for this experiment?

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…

John is going to test each sugar variable 3 times. Trials Trials refer to replicate groups that are exposed to the same conditions in an experiment. John is going to test each sugar variable 3 times.

(e) Explain how inherent variations and limitations in the measurement of experimental data lead to uncertainty in the results Candidates should recognize the relationship between variability of experimental data and the validity of any conclusions drawn. Candidates should also be able to comment on how variability and accuracy may influence the validity of conclusions drawn from experimental data.

Theories and Natural Laws Theory: a description of the world that covers a relatively large number of phenomena and has met many observational and experimental tests Law of Nature: theory (or group of theories) that has been tested extensively and seems to apply everywhere in the universe One test is worth a thousand expert opinions. Bill Nye

Collect and Analyze Results John comes up with a table he can use to record his data. John gets all his materials together and carries out his experiment.

Size of Baked Bread (LxWxH) cm3 Size of Bread Loaf (cm3) Trials Amt. of Sugar (g.) 1 2 3 Average Size (cm3) 25 768 744 761 758 50 1296 1188 1260 100 1080 1116 250 672 576 588 612 500 432 504 360 Control group

Collect and Analyze Results John examines his data and notices that his control worked the best in this experiment, but not significantly better than 100g. of sugar. John rejects his hypothesis, but decides to re-test using sugar amounts between 50g. and 100g.

Can you tell which group did the best?

Size of Baked Bread (LxWxH) cm3 Size of Bread Loaf (cm3) Trials Amt. of Sugar (g.) 1 2 3 Average Size (cm3) 50 1296 1440 1344 60 1404 1380 70 1638 1560 1612 80 1332 90 1080 1200 972 1084 Control group

Conclusion John finds that 70g. of sugar produces the largest loaf. His hypothesis is accepted*

(f) Demonstrate an understanding that a hypothesis that is consistently supported by experimental testing can become a theory. A hypothesis is a proposed explanation for an observed phenomenon, which can then be rigorously tested using scientific method. A hypothesis may be regarded as a prediction; if this is supported by experiments that confirm the hypothesis, the hypothesis may be put forward as a theory.

g) Explain the meaning of the term theory with reference to examples from the Subject Content A scientific theory is supported by a number of testable statements and is used as a general principle to explain a phenomenon. Scientific theories are intended to be accurate, predictive models of the natural world. Examples in the syllabus include the Darwin-Dana-Daly theory of atoll formation and the theory of plate tectonics

Graphs Graphs help us visualize numerical data. There are several different types of graphs: –Bar graphs –Pie graphs –Line graphs Candidates should be able to recognize trends in data presented in the forms of tables or in graphical form. For example, they should be able to recognize whether or not there is a relationship between two variables and to comment on this in the context of a stated hypothesis.

IF….THEN If = independent variable Then = dependent variable What is being manipulated (basis of your hypothesis) Control group: your experiment WITHOUT this group X axis Then = dependent variable What you’re measuring Y Axis

Qualitative vs Quantitative Just as it’s necessary to observe, it’s also important to quantify observations in some way For example: define “tall”

Bar Graphs Bar graphs are used to show a comparison of multiple objects.

Pie Graphs Pie graphs are used to compare the parts of a whole.

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

Right from Wrong The theory of gravity, theory of electricity, the germ theory of disease, and the theory of evolution are tested, accepted explanations for events that occur in nature. Theories can really never be completely proven, only disproven. When new evidence comes along, we must modify our theory or at times even get rid of it and start over again

The Need for Statistics How do you tell a really odd but correct result from a WRONG result? The simple answer is: you can never tell for certain that a given result is “wrong”. All we can do is determine whether a given result is likely or unlikely. There are 2 ways of getting a weird statistical measurement: an unusual result from the correct theory, or a result from the wrong theory. These are indistinguishable; because of this fact, statistics is never able to discriminate between true and false with 100% certainty.

Reasonability What is a “reasonable” result is subjective and arbitrary. For most work (and for the purposes of this class), a result is said to not differ significantly from expectations if it could happen at least 1 time in 20. That is, if the difference between the observed results and the expected results is small enough that it would be seen at least 1 time in 20 over thousands of experiments, we “fail to reject” the null hypothesis. For technical reasons, we use “fail to reject” instead of “accept”. “1 time in 20” can be written as a probability value p = 0.05, because 1/20 = 0.05. Another way of putting this. If your experimental results are worse than 95% of all similar results, what you measured was very unlikely.

Critically Thinking Identify and evaluate premises and conclusions in an argument Analyze conclusions based on evidence versus those based on value judgments Assign weight to opposing viewpoints based on chains of reasoning, sources of information (reliability) Adjust weighting depending on relevance to central issue, lack of specific evidence or contradictions