Scientific Investigations Equipped with his five senses, man explores the universe around him and calls the adventure Science. -Edwin Powell Hubble

Types of Investigations 1.Descriptive Investigation: involves describing and/or quantifying parts of a natural or man-made system 2.Comparative investigation: involves collecting data on different organisms/objects/features, or collecting data under different conditions (e.g. times of the year, temperatures, locations) to make a comparison 3. Experimental investigation: involves designing a fair test in which variables are actively manipulated, controlled, an measured in an effort to gather evidence to support or not support a casual relationship

Which type are these? Classify these investigations as descriptive, comparative, or experimental. ____ The effect of UV radiation on yeast survival is measured ____ Brain scans show how the brain responds to different types of music ____ A researcher records the number of lizards that are present in 10 square miles of desert E C D

Experimental Investigations Step 1: Research – Research can be done in two ways 1.Academic research – you can look in books and scientific journals to see what is already known about the subject. 2.Observations – Looking at a situation carefully – watching what is happening, and wondering why or how something works.

Observations Watch the basketball video and OBSERVE how many times the players in the white shirts pass the ball __________________ Count together as a class how many times the players in the white shirts pass the basketball _______________________ Do you OBSERVE anything else going on in the video? ________________________ Make sure to watch it a second time too!

Types of Observations-- QUANtitative Observations: Describe the characteristics of an object. These observations do not involve numbers QUALitative Observations: Involve measurements and numbers

Types of Observations-- You Try: Write an N next to the quantitative observations and an L next to the qualitative observations. ____ 1. Has a crystalline structure ____ 2. Gives off a purple flame ____ 3. Reacted for 38.5 seconds ____ 4. Occupies a volume of cm 3 ____ 5. Produces a strong odor when combined with sulfur ____ 6. Has a pH of 7.5 L L N N L N

Step 2: Purpose – The question of interest, what you are trying to find out based on your research Step 3: Hypothesis – an idea to work from, an educated guess which stems from your observations. Hypotheses have to be testable to be good hypotheses.

Put a check next to the hypotheses that are testable: ____ If pH is decreased, then enzyme activity will decrease ____ If puppies eat fancier food, they will be happier ____ If more trees are planted, then Austin will be more beautiful ____ If students listen to more music, their test scores will be higher  

Step 4: Procedure – how to do the experiment, should include detailed instructions. A valid experiment should have the following: Independent Variable: The condition that is changed by the investigator. Also known as the experimental variable. Dependent Variable: The condition that is measured by the investigator.

Number of illnesses over time Experimental setup – A setup where the independent variable has been changed. Control setup – A setup where the independent variable has NOT been changed. This setup is used for comparison. Constants – All other variables should remain the same, or constant, if possible. Error often results when other variables are not kept constant. Patients given antibiotic Patients given placebo Week Week Week Week

Question of Interest: How does the acidity of local rainwater affect the average number of frog offspring? What is the independent variable? What is the dependent variable? What would be a valid control setup? The pH of the rainfall The average number of offspring Frogs at standard conditions

Step 5: Results – Data – information collected. A valid experiment should have a large number of trials. More data = more accuracy. Data Analysis– interpretation of data (graphs, percent error, percent yield, linear regression)

Step 6: Conclusions – Report your findings. Did your data support your hypothesis? What are some sources of error in your experiment?

Scientific Law vs. Theory 1. Scientific Law : a statement describing an observed regularity. Laws describe rather than explain. A law may be either quantitative or qualitative. It must describe evidence that has been gathered using acceptable scientific standards.

Scientific Law vs. Theory 2. Scientific Theory: The most logical explanation of why things work the way they do. A theory is a former hypothesis that has been tested with repeated experiments and observations and found always to work.