Scientific Investigations

• Tell the difference between observations, inferences, and a hypothesis.

• Describe qualitative and quantitative data used in scientific investigations.

• Find the different variables and constants in an experiment.

• Explain the difference between a scientific theory and a scientific law.

• Use graphs and tables to analyze data and make conclusions.

Key Vocabulary

Hypothesis

An educated guess or a testable prediction, often structured as an "If, Then" statement.

Qualitative Data

Information that describes qualities or characteristics, observed using the five senses, such as color or texture.

Quantitative Data

Information that involves a measured quantity or amount, always represented by numbers, like length or mass.

Independent Variable

The single factor that a scientist intentionally changes in an experiment to observe its effect.

Dependent Variable

The factor that is measured or observed as the result of changes to the independent variable.

Constants

All the factors and conditions that are intentionally kept the same throughout all parts of an experiment.

Observation

• ​It is the process of gathering information using your five senses.

• ​​This focuses on exactly what you can see, hear, touch, smell, or taste.

• ​For example, you might observe that the plant's leaves are brown and dry.

Inference

• ​This is an explanation or conclusion that is based on your observations.

• ​​You use your previous knowledge and experiences to make a logical guess.

• ​For example, you might infer that the plant needs to be watered.

Qualitative Data

• ​Qualitative observations describe the qualities or characteristics of something using your five senses.

• ​​These observations are described with words and do not involve numbers or measurements.

• ​For example, observing that tomatoes are red is a qualitative observation.

Quantitative Data

• ​Quantitative observations describe the amount of something and are always expressed as a number.

• ​​These observations are made using tools to measure a specific quantity.

• ​For instance, stating that there are seven apples is a quantitative observation.

Hypothesis, Theory, and Law

Hypothesis

• An educated guess or prediction for a single, specific event.

• It is based on your initial observations before an experiment.

• It can be tested by a single experiment.

Scientific Theory

• A detailed explanation for why something in nature happens.

• It is based on many hypotheses that have been proven correct.

• It is verified many times and is widely accepted by scientists.

Scientific Law

• A statement of fact that describes a pattern in nature.

• It is considered to be true and universal in specific conditions.

• This describes what happens, but it does not explain why.

Designing a Fair Test

Independent Variable

• ​This is the one variable that you will intentionally change or test.

• ​​It is the 'cause' in a cause-and-effect relationship in an experiment.

• ​For example, using different types of paper to build an airplane.

Dependent Variable

• ​This is the variable that you will measure or observe for results.

• ​​It is the 'effect' or the data that you will be collecting.

• ​For example, measuring the distance the paper airplane flew through the air.

Constants

• ​These are all the factors you must keep the same during testing.

• ​​Keeping variables constant ensures that the results of the test are fair.

• ​For example, the paper size and airplane design must not be changed.

Graphing and Interpreting Data

• Graphs help you visualize relationships between variables in an experiment.

• The independent variable (IV) is always plotted on the horizontal x-axis.

• The dependent variable (DV), your collected data, goes on the vertical y-axis.

• Use bar graphs when the independent variable is a category, not a number.

• Observations are gathered with the five senses; inferences are conclusions from observations.

• Qualitative data is descriptive, while quantitative data is numerical.

• A fair test changes the independent variable to measure the effect on the dependent variable.

• A hypothesis is a specific, testable prediction for an experiment.

• A scientific theory explains why something happens; a scientific law describes what happens.

• The independent variable is on the x-axis, and the dependent variable is on the y-axis.