What is Science? Science is an organized way of attempting to understand the natural world, structurally and operationally. We are always: - looking for ways to improve our quality of life - trying to understand how systems work - attempting to improve on an existing system - atlatl, pump toothpaste

The Need for Proof Evidence is based on observations. Information gathered using the senses during an observation is called data (sing. datum).

Data Data can be qualitative or quantitative. –Qualitative – no specific number, rather a comparison or estimate ex. big, blue, some, herd, bunch –Quantitative – specific number given in an attempt at exacting detail ex. 21.6m, 662miles, 13, 17 reindeer

Give me some of your french fries. A.Qualitative B.Quantitative

Get a dozen eggs at the store. A.Qualitative B.Quantitative

The game costs only a few dollars. A.Qualitative B.Quantitative

There are nine cows in the field. A.Qualitative B.Quantitative

Go get some firewood. A.Qualitative B.Quantitative

Accuracy & Precision in Measurement

Accuracy & Precision Accuracy: –How close you are to the actual value –Depends on the person measuring –Calculated by the formula: % Error = (YV – AV) x 100 ÷ AV Where: YV is YOUR measured Value & AV is the Accepted Value Precision: –How finely tuned your measurements are or how close they can be to each other –Depends on the measuring tool –Determined by the number of significant digits

Accuracy & Precision Accuracy & Precision may be demonstrated by shooting at a target. Accuracy is represented by hitting the bulls eye (the accepted value) Precision is represented by a tight grouping of shots (they are finely tuned)

Accuracy & Precision Precision without Accuracy No Precision & No Accuracy Accuracy without Precision

Accuracy - Calculating % Error How Close Are You to the Accepted Value (Bull’s Eye)

Accuracy - Calculating % Error student measured the room width at 8.46 m accepted value was 9.45 mIf a student measured the room width at 8.46 m and the accepted value was 9.45 m what was their accuracy? AV)AVUsing the formula: % error = (YV – AV) x 100 ÷ AV AV is the accepted value –Where YV is the student’s measured value & AV is the accepted value

Accuracy - Calculating % Error YV = 8.46 mSince YV = 8.46 m, AV = 9.45 m 8.46 m% Error = (8.46 m – 9.45 m) x 100 ÷ 9.45 m m = m x 100 ÷ 9.45 m -99 m = -99 m ÷ 9.45 m % = % Note that the meter unit cancels during the division & the unit is %. The (-) shows that YV was low The student was off by almost 11% & must remeasure Acceptable % error is within 5%Acceptable % error is within 5%

remeasure -5% 5% remeasure Acceptable error is +/- 5% Values from –5% up to 5% are acceptable Values less than –5% or greater than 5% must be remeasured

Significant Digits How to Check a Measurement for Precision

Significant Digits & Precision could be measuredThe precision of a measurement is the smallest possible unit that could be measured. Significant Digits (sd) are the numbers that result from a measurement. which digits are significantWhen a measurement is converted we need to make sure we know which digits are significant and keep them in our conversion All digits that are measured are significant

Significant Digits & Precision How many digits are there in the measurement? All of these digits are significant There are 3 sd Length of Bar = 3.23 cm cm What is the length of the bar?

Significant Digits & Precision If we converted to that measurement of 3.23 cm to  m what would we get? Right!  m How many digits in our converted number? Are they all significant digits (measured)? Which ones were measured and which ones were added because we converted? If we know the significant digits we can know the precision of our original measurement

Significant Digits & Precision What if we didn’t know the original measurement – such as hm. How would we know the precision of our measurement. The rules showing how to determine the number of significant digits is shown in your lab manual on p. 19. Though you can handle them, they are somewhat complex.

An estimation or prediction based on previous experiences or observations are called inferences You can infer about whether or not a fish with large, sharp teeth eats other fish because of your previous experiences or observations of fish with large, sharp teeth.

Hypothesis “Educated guess” Testable prediction Possible explanation of an experience or observation in nature Always as a statement, never as a question There may or may not be an underlying knowledge about the hypothesis

Theory Best possible scientific explanation of an experience or observation in nature. Have not been tested Can not be tested There is an underlying knowledge about a theory, both observationally and experimentally

Scientific Law Always true Can not be circumvented or broken

Evidence suggests that birds may have descended from therapsid dinosaurs. A.Hypothesis B.Theory C.Law

Energy can be transformed from one form to another. A.Hypothesis B.Theory C.Law

My dog will eat all kinds of cheese. A.Hypothesis B.Theory C.Law

Gravity affects all objects in the universe. A.Hypothesis B.Theory C.Law

Tide brand laundry detergent gets your clothes cleaner. A.Hypothesis B.Theory C.Law

RIGHT or WRONG? GOOD or EVIL? Ethics and Values in Science Ethics refer to whether or not an action or plan is considered right or wrong by a group or society. Your values, which differ from person to person, help you decide whether or not something is ethical. Ex. charging for cures, man v. environment

The Scientific Method An organized procedure to determine whether or not a statement (or idea) is valid. Every scientist follows the scientific method, but not every scientist uses all of the scientific method.

The Scientific Method Determine the Problem –Ask a question that you would like answered about a particular topic Gather data Research your topic using observations or other sources of data (books, magazines) Make a hypothesis –Make a statement concerning your topic Must be testable can not be a question

The Scientific Method Experiment –Test your hypothesis in a controlled experiment setting Analyze Results –Use the data from your experiment to support your hypothesis Conclusion –A restatement of the hypothesis that takes the results of the experiment into account –The data may not support the hypothesis

Which step of the Scientific Method is a testable statement? A.Determine the Problem B.Analyze Results C.Experiment D.Hypothesis

Which step of the Scientific Method proves or disproves the Hypothesis? A.Gather Data B.Analyze Results C.Experiment D.Conclusion

Which step of the Scientific Method has us research the work done on our question by others? A.Determine the Problem B.Gather Data C.Experiment D.Conclusion

Which step of the Scientific Method is a restatement of the Hypothesis? A.Gather Data B.Analyze Results C.Experiment D.Conclusion

Which step of the Scientific Method has us make graphs and charts to determine the outcome of our Experiments? A.Gather Data B.Analyze Results C.Experiment D.Conclusion

Controlled Experiments Have at least two groups: Control Group Used to see what happens when nothing is changed As many variables are kept the same as possible Experimental Group Only one variable is changed Can be more than one group, changing the same variable

Variables Control variable –Kept the same from group to group, trial to trial

THE CAUSE Experimental Variable –Also called the Manipulated variable, the Independent variable –Condition changed from the control group to elicit a response

THE EFFECT Dependant Variable –The outcome of the changed variable –What changed because of what you changed for the experimental group

Reproducible Results To be considered valid, a successful experiment must be replicable (repeatable). –Scientists often publish their lab reports in journals so that other scientists can try these experiments. Make certain that the hypothesis you declare is based on a clear cause-and-effect relationship.

What may have gone wrong? If the Results and Conclusions do not support your hypothesis, check your procedures for any sources of error. Sources of error can be included in laboratory report to help other scientists determine what may have gone wrong in your experiment.

Which variable do you make certain does not change for the experiment? A.Control Variable B.Experimental Variable

Anything that may have affected your data in an experiment should be described under which part of a lab report? A.Premise B.Procedures C.Sources of Error D.Conclusion

Any data which does not seem to follow the other data in an experiment could be caused by A.Faulty equipment B.Human error C.Flawed chemicals/subjects D.All of the above

Which variable do you change for the experiment? A.Control Variable B.Experimental Variable

A sample Scientific Investigation To prove or disprove the hypothesis, run an experiment Make sure that the experimental (independent) variable is the only one that changes

A sample Scientific Investigation Define the question –Does smoking cause cancer? Gather Data –Ask doctors, hospitals, people in cancer wards Make a hypothesis –Smoking causes cancer HERE COME THE LAWSUITS!

Experimental Group Control Group Number of subjects Control variables Experimental Variable Number of subjects affected Correlation?

Analysis of Results Hypothesis disproved –If smoking causes cancer, all subjects should have gotten cancer –Some of the control group developed cancer for no apparent reason

Conclusion Smoking does not cause cancer Surgeon General’s warning –Because of the high correlation, you can restate your hypothesis with strong conditional wording –Smoking greatly increases the risk of cancer, emphysema, pregnancy complications, etc.