The Scientific Method A review

What is the ``scientific method''? Organized common sense! 1. Make observations. 2. Invent a tentative description, called a hypothesis, that is consistent with what you have observed. 3. Design an experiment to test the hypothesis. 4.Collect Data, Analyze 5. Conclusions : what you learned from the experiment 6. Repeat/Retest : multiple trials are necessary

Simplified … Make observations (vs inference) Write testable hypothesis Design experiment (dependent/ind. variables) Collect data (qualitative vs quantitative) Graph and analyze results

Observations o OBSERVATION: The use of senses to see and record the world around you. o INFERENCE: Making a conclusion based on opinion or prior experience.

Hypothesis A statement that attempts to answer the experimental question. No longer referred to as an ‘educated guess’; instead, it is a proposed solution. Hypothesis must be TESTABLE.

Are these good hypotheses? Fresh-water fish taste better. The more expensive a perfume is, the better it smells. Crocodiles in the Amazon Rain Forest have higher reproduction rates than those in the Florida Everglades. Red cars have a higher resale value than cars of other colors.

Dependent vs. Independent Variables Independent Variables—You control or change; aka “manipulated” variable. Dependent Variable—You cannot control; aka “responding” variable. Dependent Variable depends on the independent variable. You measure the dependent variables All other factors are held constant (not changed)

Identify the variables. 1) The amount of cracking and peeling in paint was measured at different temperatures. 2) Mice bite each other more frequently when they are crowded in the cage. 3) The number of letters recognized on an eye chart is determined by how far away the chart is. 4) Ropes of different diameters will hold different amounts of weight before breaking. 5) Lemon trees receiving the most water produce the largest lemons.

Data Table Construction 1. Organize important categories of information into columns. 2. Label columns using appropriate units. 3. Title should reflect contents of data table.

Collecting data quaLitative data = color, texture, odor, etc. qua N titative data = N umeric information (49 o F 6.8 grams 1,479,930,110 meters) Scientific notation is used to manage very large or very small numbers.

 Accuracy: how close a number is to what it should be.  Data points close together, but incorrect = high precision, low accuracy  Precision: degree of perfection or repeatability  Data points accurate, but widely ranging = high accuracy, low precision Accuracy vs Precision

Organize data into graphs, tables. Pie chart: Useful for showing parts of a whole Parts are labeled as % so whole circle = 100%.

Bar graphs Often used to show how a quantity varies with factors such as time, location, or temperature Relative heights of the bars show how the quantity varies

What bushel price yielded the most income for the farmer?

Line Graphs The points on a line graph represent the intersection of data for 2 variables: the independent and the dependent variable Remember “DRY MIX” The Dependent (aka Responding) variable is on the Y axis. The Manipulated (aka Independent) variable is on the X axis.

Exponential Growth Curve