Scientific Method

Monday, 8/14/17 What do you think makes a good (valid) experiment? Answer this question in your notebooks: What do you think makes a good (valid) experiment? Today: 1.) “Scientific Method” notes Homework: 1.) Summer work due tonight by 11:59 PM 2.) Chapter 1 outline due tomorrow (Tuesday, 8/15)

Word of the Day Diatribe (n) A long, abusive speech or lecture. “Upset about his demotion, Ed made an angry diatribe about his employer.”

Find a Partner Decide who will be the bacterium and who will be the human

Inquiry Inquiry is the search for information and explanation Scientists begin an inquiry investigation with a question There are two main types of scientific inquiry: discovery science and hypothesis-based science 5

Discovery Science Discovery science describes natural structures and processes This approach is based on observation and the analysis of data 6

Types of Data Data are recorded observations or items of information Data fall into two categories Qualitative, or descriptions, rather than measurements Quantitative, or recorded measurements, which are sometimes organized into tables and graphs 7

Induction in Discovery Science Inductive reasoning draws conclusions through the logical process of induction Repeated observations can lead to important generalizations For example, “the sun always rises in the east” Your turn…give me an example! Starts with an observation and then forms a generalization 8

Deduction: The “If…Then” Logic of Hypothesis-Based Science Deductive reasoning uses general premises to make specific predictions For example, if organisms are made of cells (premise 1), and humans are organisms (premise 2), then humans are composed of cells (deductive prediction) Your turn again…example? 9

Partner Time Humans: describe the difference between inductive and deductive reasoning to your partner Bacteria: Review the difference between quantitative and qualitative data

Steps in the Scientific Method Observation Hypothesis Experiment Data Collection Conclusion 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 Usually 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

Experiment A good or “valid” experiment will only have ONE variable changed at a time!

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

The Control Variable The experimenter makes a special effort to keep other factors constant so that they will not affect the outcome. Those factors are called control variables.

What is the Purpose of a Control? Controls are NOT being tested Controls are 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 Controls & 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 control variable. What are other examples of control variables in this experiment?

One more thing… it is best to make several trials with the independent variable…why?

Remember: To be a Valid Experiment: Two groups are required --- the control & experimental groups What do you think the difference is between these groups? There should be only one variable manipulated

Data Results of the experiment May be quantitative (numbers) or qualitative (descriptions)

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

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

In order to verify the results, experiments must be retested.

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 and organize it 6) Form a Conclusion 7) Retest

How a Theory Develops A hypothesis may become so well-supported, scientists consider it a theory. Theories enable scientists to make accurate predictions about new situations As new evidence is uncovered, a theory may be revised or replaced by a more useful explanation

Inferences Scientists often draw inferences from data gathered during experiments. Inference- conclusion made on the basis of facts and previous knowledge rather than on direct observations. Unlike a hypothesis, an inference is not directly testable.

Accuracy vs Precision Accuracy- Getting the expected number (“accepted value”) Precision- Getting the same number multiple times

Validity vs. Reliability Validity: The degree to which a test actually measures what it is designed to measure Reliability: Repeatability of findings (consistency)