Assessing Prior Knowledge

1. Assessing Prior Knowledge 1. To make sure experimental results are valid, which of these procedures must be followed? • add bias B) communicate uncertain results C) conduct multiple trials D) pick two hypotheses

2. Validity and Reliability, Fair Test, and Generating Testable Questions • 7-1.4 Explain the importance that repeated trials and a well-chosen sample size have with regard to the validity of a controlled scientific investigation. • 7-1.2Generatetestable questions. • 7-1.3 Explain the reasons for testing one independent variable at a time in a controlled scientific investigation • 8-1.5 Explain the importance of and requirements for replication of scientific investigations. • 8-1.1 Design a controlled scientific investigation. • 8-1.2 Recognize the importance of a systematic process for safely and accurately conducting investigations.

3. What is a Fair Test? • If there is only 1 independent variable, there is only one factor that can affect the results of the experiment • What should you do before you begin? • 1. List all factors that could possibly affect the results. • 2. Choose one to be the independent variable. • 3. Decide how you are going to control all the other factors. These should be kept CONSTANT. (AKA Controlled variables)

4. Control Group-why and how • What happens if you have more than one factor affecting the test? • More than 1 variable changed = UnFair TEST = INVALID results • You cannot make a reasonable conclusion • How to avoid this: Set-up a control group • Treat this group like the experimental group EXCEPT you don’t apply the independent variable (normal/regular)

5. Experimental and Control Group Set-Up What kind of graph? __________ EX: I want to test how different fertilizers affect plant growth. • Group 1: no fertilizer (control) • Group 2: fertilizer A • Group 3: fertilizer B • Group 4: fertilizer C • Controlled variables/constants? • Plant type, container, soil, light, water, temperature, humidity, etc.

6. How to generate testable questions • Testable questions • Test one independent variable at a time • Include a dependent variable • Include the relationship of IV and DV • Can be answered through scientific investigation and data collection • Ex: Not opinions

7. Testable Question Example • How does the slope of a ramp affect the travel time of a toy car? • IV: slope/amount of slant, measured in degrees • DV: time it takes care to travel length of ramp, measured with stopwatch • What are some controlled variables? • Car, ramp, surface, timer

8. Identifying TESTABLE Questions • Is this testable? How does the paper airplane fly? • No; does not include IV and DV • To change the question so it is testable: • list some variables that you could manipulate that are involved with flight of a paper airplane • wing shape, body shape, type of paper used • Second, decide what you are going to measure (dependent variable). • Examples: Distance the plane will fly,Length of time the plane stays in the air • TESTABLE NOW? • Does changing the shape of the wing affect the distance the paper airplane will fly? • Does changing the shape of the body affect the length of time the paper airplane will stay in the air?

9. CFU- Identifying testable questions • Does changing the kind of surface affect how far my ball will roll? • Testable • IV: kind of surface • DV: distance ball rolls • Does the size of wheels affect how far my toy car moves? • Testable • IV: wheel size • DV: distance travelled • Which tastes better, Coke or Pepsi? • Not testable

10. CFU- Testable Questions? • Does laundry detergent make dirty white clothes clean? • Not testable • How does the thickness of insulation affect the temperature in a dog’s house? • Testable • IV: insulation thickness • DV: doghouse temperature • Do batteries make flashlights light up? • Not testable

11. Valid • Definition: actually supporting the intended point or claim • truthful, accurate, precise • Examples: • “Why does that work Mrs. Robbins? You should know, you’re a science teacher!” • “Yes, that is a valid point (that I’m a science teacher), but I have no idea!”

12. Investigations Need to Be Repeated • Scientists must prove (verify) their conclusions. • Why might a company ask you on the phone to verify your address or middle name? Hoaxes

13. How can scientists prove (verify) their results are valid? • Other people can repeat it doing the same procedures. • Experimental trials and tests must be repeated again and again…

14. What does it mean to repeat an experiment? • Data Collection • More than once • Under the same conditions • Room temperature, lighting, etc. • Using the same measurement tools • When possible, take measurements several times and average the results

15. When experiments are repeated what should data look like if it is valid and provable? • Experimental results should have patterns or trends. • If there is no trend or pattern, something went wrong… Valid Valid

17. How many times should you repeat an experiment? • (ex) Dice • Claim: I am so lucky, every time I roll the a die I get my favorite number 4. • Trial 1: Get a 4. Therefore I am lucky… Mr. Skeptic rushes in… “Wait! Do that a few more times and I bet your won’t get 4’s every time!”

18. How many times should you repeat an experiment? • Good rule of thumb is 3 times yourself plus someone else doing the same procedures on their own and getting the same results.

19. What happens if there is not enough repetition? • Errors in procedures or data collection may be missed or not detected.

20. Reliable? • What does it mean for a person to be reliable? • What does it mean for datato be reliable? • You get similar results each time. • The more data you have, the more reliable it is.

21. Which Experimental Data is Most Valid? Most Valid

22. Which Experimental Data is Most Reliable? Most Reliable

23. Experimental Results More Repetition = Greater Validity More Trials/Data = More Reliable

25. Hoaxes

27. Validity Recap • Repetition ensures • that the experiment is valid, • the data is reliable and can be trusted and not made up. • Validity demonstrates how close the investigation is • accurate • dependable

28. What Could Lead to Invalid Experiment Results? • Not enough trials • Improper sample size (too small)

29. What if repeated investigation produces different results? Check: • Was setup or directions followed properly? • Were similar procedures followed in exact same way? • Were appropriate tools used? And used properly? • Were measurements taken accurately? • Was data recorded correctly? (ex: 0 vs. O)

30. What is an Experimental Trial? • Trial: • Each repeated set of data • Real Life Example: • Government Safety crash tests are repeated over and over again and then used to rate the safety of cars.

31. Sampling and Estimation • Sample • small portion of the total number • used as an estimation. • proper sample sizes may result in information and conclusions that might apply to the whole group

32. How are TV Rating’s Determined? • Television ratings are determined by just 5000 (13,000 people) households. • This sample represents the television viewing habits over 270,000,000 Americans. • The sample of 5000 best reflects the composition of America as determined by the United States Census and other government organizations. The sampling is so sophisticated that each People Meter represents about 20,000 people. From that small sample comes out television ratings.

34. Scientists want to find out how effective a pesticide (insect killer) is on a protecting a 2000 acre pine tree forest from predacious beetles. How many acres of land should they observe and collect data? A) one acre B) two acres C) twenty acres D) two hundred acres. D) two hundred acres. Answer

36. Do biologists or botanists (plants scientists) study individually every single animal or plant they are studying? A) Scientists have to study all the living animals or organisms in a species to be accurate in their data collecting. B) Scientists study samples of populations because they cannot study all of them. Answer • B) Scientists study samples of populations because they cannot study all of them.

37. A pet owner did an experiment to determine which of ten brands of fish foods would produce the most growth in her fish. She placed a gold fish in each of ten different bowls and fed each with a different brand of fish food for six months. Once a week she measured and recorded the mass of each fish. Which step would have improved the experiment? A) Testing each food with more than one fish. B) Measuring the mass once a month. C) Keeping the fish in larger containers. D) Conducting the experiment for one week.

38. Which is the best hypothesis for an investigation which measures how pulse and heart rate is affected by exercise? A. If you increase the amount of pulse rate, then your exercise will increase. B. Exercise will increase Pulse. C. The athlete’s pulse rate was 120 over 70. D. If you increase the amount of exercise, then the pulse rate will increase. • D. If you increase the amount of exercise, then the pulse rate will increase. Click on the box for the answer.