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

Observationso 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. quaNtitative data = Numeric information

(49o 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 andthe 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