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

SC Indicators: Explain the importance that repeated trials and a well-chosen sample size have with regard to the validity of a controlled scientific investigation.Explain the importance that repeated trials and a well-chosen sample size have with regard to the validity of a controlled scientific investigation Explain the importance of and requirements for replication of scientific investigations.

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!”

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

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…

What does it mean to repeat an experiment? Collect Data –More than once –Under the same conditions Room temperature, lighting, etc. –Using the same measurement tools

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

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!”

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.

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

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

TrialsExperiment A Experiment B Experiment C Trial Trial Trial Trial Trial Trial Trial Which Experimental Data is Most Reliable?

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

Hoaxes

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.

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

Other Human Errors Setup or directions not followed. Wrong Tools or not used correctly. Wrong or inaccurate measurements. Different Observations were correctly made. Mistakes made recording data.

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

Sampling and Estimation Sample (small portion) of the total number –Used as an estimation.

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.

Scientists want to find out how effective a pesticide (insect killer) is on protecting pine trees 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. Click on Box to find the Answer

Honey Bee -Die-off Alarms Beekeepers -Crop Growers -Researchers Grass Shrimp -Effects of pollution and habitat destruction Galapagos Tortoises and Sea Turtles -Endangered Species What kinds of Populations do Scientists Study? Scientists Study?

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. Click on the box for the answer.

Annual Christmas Bird Count Each year during Christmas, hundreds of people participate in an annual bird count. This count is data collection. This data is used to estimate the total amount of birds in a species and whether birds are becoming endangered.

Ticket Out the Door: 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.

D. If you increase the amount of exercise, then the pulse rate will increase. Bellwork – Answer in Your Notebook 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 increases 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. Click on the box for the answer.