Types of Scientific Investigations • Different research questions require different types of investigations. • Descriptive Investigations • Comparative Investigations • Experimental Investigations
Descriptive Investigation: • Involves describing and/or quantifying parts of a natural system. • Example – observing cells under a microscope and diagramming what is seen. • Has a research question, procedures, and conclusion • Used when little is known about the topic • No hypothesis or prediction • Key words: Observe, describe, list, identify
Comparative Investigation: • Involve collecting data on collecting data on different populations/organisms, under different conditions (ex. Times of year, locations), to make a comparison. • Has a research question, possible hypothesis, procedures, and conclusion. • Can have independent/manipulated and dependent/response variables • No control / control group • Key words: Compare/contrast, similarity/difference, categorize
*Most scientific investigations you do in science class will be experimental investigations
Experimental Investigations Have Variables • Independent Variable – the part of an experiment that you manipulate or change • Dependent Variable – the part of an experiment that responds to the change you made. Measure it! • Control – the part(s) of an experiment that you want to stay the same all the time
Experimental Investigation: • Involves a process in which a “fair test” is designed in which variables are actively manipulated, controlled, and measured in an effort to gather evidence to support or refute a causal relationship. • Example- Testing the height of a ramp to determine how far a marble will roll. • All known variables have been identified • Has a research question, hypothesis, procedures, control, and conclusion • Has independent/manipulated and dependent/response variables • All factors can be held constant except the manipulated
Graphs in Experimental Investigations • Turn a data table into a picture • Show trends (patterns) in the data • Make results easy to see
Pie Chart (Pie Graph)h) • Shows percentage out of 100 • Often used in polls and surveys • Colors and patterns differentiate data
Bar Graph • Compares groups to one another • Uses rectangular bars or pictures • Colors and patterns differentiate data
Scatter Plot (Line) Graph • Data points connected by straight lines • Shows change in data (usually over time) • Line of best fit (curve) shows trend in data • Most of the graphs you make in science class are scatter plot graphs with a line of best fit (curve)
Labeling a Graph – an Example • Graphs have labels • Title – Distance-Time Graph • X-axis (horizontal, flat axis) - Time • Y-axis (vertical, up and down axis) - Distance • Number values – x-axis: 1,2,3 and y-axis: 10,20,30 • Units – meters (m), seconds (s) / s
What type of Investigation Is it? (Practice scenarios) Identify the type of investigation described and justify your choice.
Scenario #1 _____________ Investigation You count how many prickly pear cacti are growing in a field and record the number of pads on each plant.
Counting Prickly Pear Pads is DESCRIPTIVE •What is your research question? •Do you have a hypothesis? Why or why not?
Scenario #2 _____________ Investigation You take two boxes of breakfast cereal, extract the iron from both boxes and look at the differences in iron content.
Iron in Different Cereals is COMPARATIVE •What data are you collecting? •What are you comparing? •Do you have a question? •Do you have a hypothesis?
Scenario #3 _____________ Investigation Using the same engine model, you test different types of oil to see which one keeps the engine lasting the longest at 50 miles per hour.
Oil Effectiveness at 50 mph is EXPERIMENTAL •What is your variable? •What are your controls? •What is your hypothesis?
Scenario #4 _____________ Investigation A new star is observed in the Andromeda Galaxy. Observations and data are collected on this new star.
Andromeda Star is DESCRIPTIVE •What kind of data can you collect?
Scenario #5 _____________ Investigation Park rangers count the number of rattle snakes observed along a specific trail at different times during the year. They use this information to let campers know when it is safer to go off the path.
Snakes on a Trail is COMPARATIVE •What is being compared? •What is the independent variable? •What is the dependent variable? •What could be a hypothesis?
Scenario #6 _____________Investigation You observe how the diameter of a splash changes as you drop a marble from different heights into a pan of water.
Splash Diameter is EXPERIMENTAL •What are you measuring? •What is the variable you are changing? •What are your controls? •What is the potential causal relationship? •What could be your hypothesis?
Homework time! Now….it’s time to do classify the three investigations that were given to you in class today.