The Scientific Method & Experimental Design

What is Inquiry? Begins with observations you make about the natural world, followed by a question. What is causing that? Use a variety of methods to answer the questions you raise Lab & field investigations, models, simulations, data sets Scientific method of investigation is cyclic, not linear…why?

The Scientific Method: Make Observation Statement of problem, ask a question Hypothesis: propose a tentative answer Design & conduct an experiment (Use quantifiable data  math is extremely important) Use statistical tests to evaluate the significance of your results (Χ2 test, null hypothesis) Acceptance or rejection of hypothesis.

Data Are recorded observations Can be quantitative or qualitative Figure 1.24

The Role of Hypotheses in Inquiry In science, a hypothesis Is a tentative answer to a well-framed question, an explanation on trial Makes predictions that can be tested

We all use hypotheses in solving everyday problems Observations Questions Hypothesis # 1: Dead batteries Hypothesis # 2: Burnt-out bulb Prediction: Replacing batteries will fix problem Replacing bulb Test prediction Test does not falsify hypothesis Test falsifies hypothesis Figure 1.25 We all use hypotheses in solving everyday problems

A Closer Look at Hypotheses in Scientific Inquiry A scientific hypothesis must have two important qualities It must be testable It must have the potential of being rejected "No amount of experimentation can ever prove me right, one single experiment can prove me wrong." --- Albert Einstein.

Designing Controlled Experiments In controlled experiments we start with two (or more) groups that are as similar as possible and we devise a method to manipulate only ONE variable. Independent Variable =the variable that is manipulated Dependent Variable = the response that is measured

Null Hypothesis The premise that any observed differences are simply the result of random differences When quantified observations, or data, are collected, statistical methods are used to calculate the likelihood that the null hypothesis is correct.

Science as a process of inquiry AP Biology Science as a process of inquiry Built on repeatable observations & testable, falsifiable hypotheses

AP Biology Falsifiable A hypothesis is falsifiable if you can design and perform and experiment to show you that it is wrong, if it is wrong (meaning, it can be tested). EXAMPLES: Falsifiable – Increasing the amount of water given to a plant will increase its growth NOT Falsifiable – Giving a plant more water will make it happier. Inherently disprovable

Data Tables & Graphing Review

Working with DATA When you work with data during an experiment, you need to: Make accurate and precise measurements. Account for error in measured values Develop techniques and consistency for collecting data Understand the units and properties of the data. Make observations of trends and patterns in the data. Produce visual representation of data, GRAPHS and CHARTS.

What type of graph is best/most commonly used in scientific research? LINE GRAPH!!!!

Introduction to Graphing Techniques

Introduction to Graphing Techniques Identify the independent and dependent variable. The independent variable is carefully controlled and varied by a specific amount during an experiment. It is plotted on the x-axis. The dependent variable must be measured every time the independent variable is changed during the experiment. It is plotted on the y-axis. Choose your scale carefully (must be consistent intervals). Make your graph as large as possible by spreading out the data on each axis Do not number every grid on your axis.

Intro to Graphing Techniques cont. Label each axis with the name of the variable and the units of measure. Title your graph. The title should be short and clearly state the purpose of the graph. The title could include the independent and dependent variables. General the titles are written as the y variable vs. the x variable.

Direct Relationship

Inverse Relationship

Designing a Controlled Experiment You may work with ONE partner in this activity to review the components of a controlled activity. Each student must complete their own data. At the end, you will practice designing your own controlled experiment.