What Science Is

Dr. Moody

How Science Works• Science is the systematic study of the

observable world (= natural phenomena) and how it works.

• How do we gather information/knowledge?

1. Make careful and thoughtful observations

2. Through inference

• Inference: A conclusion reached on the basis of evidence or reason

Types of Inference (Reasoning)

• Inductive Inference: Arriving at a conclusion based on repeated observation. – Repeated observation of the phenomenon

supports my hypothesis. – The sun came up yesterday and today, so I predict

it will come up tomorrow. • Can only say that our conclusion is probably

true.

Types of Inference (Reasoning)

• Deductive Inference: Logical process of using accepted facts to draw conclusions.

• Expressed using syllogisms:

If A then B (Premise)

A (Premise)

therefore, B (Conclusion)

• Problem: If the premises are not true, then the conclusions might be wrong.

1. All men are mortal. Socrates is a man, therefore Socrates is mortal.

2. All mammals are warm-blooded. All dogs are warm-blooded. Therefore, all dogs are mammals.

3. All people sweat a lot after they run a marathon. You are sweating a lot. Therefore, you must have just run a marathon.

Scientific Inquiry• Scientific inquiry: ways by which scientists study

the natural world and propose explanations for natural phenomena based on evidence derived from their work.

• Use of critical, logical, and creative thinking skills to raise and engage questions of interest.

• Requires:

– Objectivity

– Skepticism

Critical Thinking and Science• Critical thinking is the deliberate process of

judging the quality of information before accepting it.

• Critical thinking should be a part of your everyday life:– When listening to the media

– Surfing the internet

– Listening to me, reading textbooks, etc.

– HOWEVER: YOU MUST BE KNOWLEDGEABLE ABOUT A SUBJECT BEFORE YOU CAN EFFECTIVELY DISCUSS IT!

The Scientific Method(or the 7 steps of scientific inquiry)

The Question1) Explore a phenomenon

– Make observations– What do you know about the phenomenon?– What do others know about the phenomenon?

2) Focus on a question– Construct a question to investigate based on your

observations– Is the question testable?– Construct a hypothesis (more on this later)– State a prediction

Hypotheses

• A hypothesis is a testable explanation for a natural phenomenon.

• Hypotheses are formed based on observation and current theory (using inductive or deductive reasoning).

• Often stated as an “If…then…” statement

Example: Effects of fertilizer and light on plant growth

The Procedure3) Plan the experiment/investigation

– What data needs to be collected? – What are the variables and constraints?– What will serve as a control for comparison?– What materials are required?

4) Conduct the experiment/investigation– Conduct the experiment as planned– Collect data– Record data– Graph results

The Scientific Method(or the 7 steps of scientific inquiry)

The Results5) Analyze the Data and Evidence

– Interpret and make meaning from the data – Look for patterns and relationships among variables– Analyze the data and evidence and determine the

validity of your hypothesis (supported or rejected?)– Make a claim based on your evidence

6) Construct New knowledge– Form an explanation (model) from the claim and

supporting evidence– Connect your new knowledge to your prior

knowledge and the knowledge of others (existing theories)

The Scientific Method(or the 7 steps of scientific inquiry)

The Results (continued)7) Communicate New Knowledge

– Discuss your results and conclusions with others– Use scientific reasoning skills to link your claim

and supporting evidence– Engage in scientific argumentation, allowing

others to critique your experiment/investigation and claim, and provide counterarguments to your findings.

– Consider follow-up questions for investigations

The Scientific Method(or the 7 steps of scientific inquiry)

Communicating New Knowledge

• Research must be reported to the scientific community, generally as a paper in a scientific journal.

• Scientific research is thoroughly reviewed by other scientists (peer review)

• If the research has been carefully carried out using the scientific method then it can be published and becomes part of the primary literature (“so and so published a paper in the Journal of Blah Blah Blah”).

Scientific Argumentation1) Question

– Stems from observation & guides investigation

2) Claim– Your tentative conclusion– From prior knowledge and assumptions

3) Evidence– Data that supports or refutes your claim/hypothesis

4) Explanation– Explain your claim based on your new data/knowledge

5) Rebuttal– Questions regarding the reasoning used and the validity

of your evidence. – Counterclaims (data can be interpreted in multiple ways!)

Theories and Laws

• Laws describe how a system behaves (e.g., the law of gravity).

• Theories explain those laws.

• In our everyday use of the word, it often means “imperfect fact” or “speculation.”

• In science, a theory is something VERY SPECIFIC!!!

Theories and Laws• A scientific theory is something that has been

tested many different times, in many different ways, and has not yet been disproved.– Theories are supported or rejected by testing

hypotheses.

– Theories can change!

• HOWEVER, theories are rejected ONLY when they:– Are replaced by new theories that explain

predictions of the old theory

– AND make new predictions!

How Science Works• Society’s traditional views of nature sometimes

differ with scientific findings (e.g., Capernicus’ heliocentric model and Galileo).

• You have to remember that science can only describe and attempt to explain the physical world.

Veritasium Clip

• “Can You Solve This?”

http://www.youtube.com/watch?v=vKA4w2O61Xo&app=desktop

Science vs Pseudoscience• “Pseudo” = false• The only way to spot a fake is to know as much as

possible about the real thing!

Science vs PseudoscienceScience…

• Results are verifiable and can be reproduced

• Clear what methods were used to reach conclusions

• Focus on failed predictions of a theory

• Progresses; more and more is learned about the process under study

• Convinces by appeal to evidence

• No conflicts of interest; no personal financial stake in results of scientific studies

Pseudoscience…• Results are not verifiable and

cannot be reproduced• Methods are often unknown• Failed predictions are

ignored, excused, or even hidden and lied about

• No progress is made; nothing concrete is learned

• Convinces by appeal to belief or faith

• Pseudoscientists often earn some or all of their living selling their “services”

Scientific Experiments• Used to test hypotheses

• Conducted under carefully controlled conditions. where experimental variables can be controlled.

• Ideally, conditions should be the same for all groups except the variable you are interested in.

• Researcher changes one variable (independent variable) and observes or measures the result (the dependent variable).

Scientific Experiments

• The independent variable is the variable the scientist changes in the experiment

• The dependent variable is what the scientist measures in the experiment

• A control group is a group in which no changes are made. It used as a standard for comparison.

• An experimental group is subjected to the same conditions as the control group except for the variable(s) being studied.

Qualitative vs Quantitative Data

• Qualitative Data– Deals with descriptions (qualitative = quality)– Data that can be observed but not measured– E.g.) colors, textures, smells, tastes, appearance,

relative size, etc. • Quantitative Data

– Deals with numerical descriptions (quantitative = quantity)

– Data that can be measured– E.g.) length, height, area, volume, mass, temperature,

time, velocity, etc.

Back to our plant growth experiments…

Fertilizer Experiment

Work in pairs to complete the following: 1) State a hypothesis2) State a prediction3) Identify the experimental groups4) What could be used as a control group? 5) Identify the dependent variable6) Identify the independent variable

Dr. R.M. Moody

Sampling Error in Experiments

• It is important to conduct multiple trials with each independent variable. This is called replicaton.

• Researchers cannot typically survey an entire population, and must instead rely on data collected from a subset of the population (thank goodness for statistics!).

• Sampling errors occur when conclusions inferred from the subset differ from results from the whole population.– Sampling errors occur most often when sample sizes are small.– Selecting a larger population subset or repeating the experiment

many times reduces sampling error.

Dr. R.M. Moody

A) Natalie, blindfolded, randomly plucks a jelly bean from a jar. There are 120 green and 280 black jelly beans in that jar, so 30 percent of the jelly beans in the jar are green, and 70 percent are black.

B) The jar is hidden from Natalie’s view before she removes her blindfold. She sees only one green jelly bean in her hand and assumes that the jar must hold only green jelly beans.

C) Blindfolded again, Natalie picks out 50 jelly beans from the jar and ends up with 10 green and 40 black jelly beans.

D) The larger sample leads Natalie to assume that one-fifth of the jar’s jelly beans are green (20 percent) and four-fifths are black (80 percent). The sample more closely approximates the jar’s actual green-to-black ratio of 30 percent to 70 percent. The more times Natalie repeats the sampling, the greater the chance she will come close to knowing the actual ratio.

Here’s an example with two experimental variables…

Dr. R.M. Moody

Example: Predation on butterflies by birdsResearchers observed the behavior of peacock butterflies with and without predators in the wild:

– When a peacock butterfly rests in the absence of predators, it folds its wings so only the dark underside shows.

– When a butterfly sees a predator, it repeatedly flicks its paired forewings and hindwings open and closed, a movement that both makes wingspots visible and produces hissing and clicking sounds.

Dr. R.M. Moody

Example: Predation on butterflies by birds• Hypothesis 1:

– Butterflies with wing spots will be consumed less often by birds.

– How to control? Paint the spots.

• Hypothesis 2:– Butterflies that produce noise with their hindwings will be

consumed by birds less often those that do not.

– How to control? Remove the sound-producing structures of the hindwings

• Each butterfly was then placed in a large cage with a hungry bird (blue tit). The same cage was used for all trials.

Dr. R.M. Moody

Example: Predation on butterflies by birdsIndependent

VariablesDependentVariables

Dr. R.M. Moody

Results and Conclusions• Predation experiments revealed that birds are,

indeed, deterred by peacock butterfly sounds, and even more so by wing spots.

• The presence of eye spots and sound-production significantly reduce butterfly predation by birds.

• This study provides evidence that eye spots and sound production evolved as anti-predatory traits.

Your turn…

Vitamin C and Cancer in MiceIt has been suggested that vitamin C supplements lower the risk of cancer in mammals. You are given 100 mice that have been bred to have an identical genetic make-up. You are asked to design an experiment to address the question of whether vitamin C lowers the risk of cancer in mice.

--Form a hypothesis--State a prediction--Design an experiment to test your hypothesis--Identify the following:

Control group, treatment group, independent variable, and dependent variable

Dr. R.M. Moody

Graphs• Graphs help you interpret and communicate

your results. • Graphs show the relationship between your

dependent and independent variable. – Independent variable: What you change– Dependent variable: What is measured– Type of graph used dependents on the type of data

being presented: – Example: Continuous vs Discrete (categorical) Data

Dr. R.M. Moody

Graphing Scientific Data• Continuous or Chronological (=time) Data:

– Effect of temperature on growth rate– Change in stock value through time – Use a line graph or scatterplot

• Discrete (Categorical) Data:• Whenever displaying categorical data or averages:

– Number of species per amount of area sampled– Mean shell thickness of gastropods at multiple

study sites– Presence/absence of traits – Use a bar graph

Graphing Practice