SCIENTIFIC SCIENTIFIC METHODMETHOD

The way we The way we (scientists)(scientists) do things.do things.

• Scientists have a unique way of looking at the world.

• They want to know more about their world.

• They follow a set of rules for governing their research.

OBSERVATIONSOBSERVATIONS

► All of us make All of us make everyday everyday observations.observations.

► Observations lead to Observations lead to questions about the questions about the world around us.world around us.

► Scientists want Scientists want answers to these answers to these questions. questions.

OverviewOverviewObservation

Hypothesis

Experiment

Control Group + Experimental

Group

Results

Evidence supports the hypothesis

Evidence inconsistent with the hypothesis

Revise Hypothesis

Repeat the Experiment

Scientific Theory

Problem StatementProblem Statement

► A problem statement A problem statement states the question states the question raised by raised by observations.observations.

► Problem statements Problem statements often begin with often begin with “why” or “how” or “why” or “how” or “what if.”“what if.”

ResearchResearch► Maybe someone already Maybe someone already

knows the answer to your knows the answer to your question.question.

► Sources include:Sources include:► - Past relevant experiments- Past relevant experiments► - Encyclopedias- Encyclopedias► - Scientific Journals- Scientific Journals► - RELIABLE Online - RELIABLE Online

ResourcesResources

► Must be in your OWN Must be in your OWN WORDSWORDS

► Proper Citing is important! Proper Citing is important! Give credit where it is dueGive credit where it is due

HypothesisHypothesis

► A hypothesis states A hypothesis states what the scientist what the scientist believes to be the believes to be the answer to the problem answer to the problem statement.statement.

► A hypothesis draws on A hypothesis draws on all the background all the background known about the known about the problem.problem.

► Hypotheses are Hypotheses are formatted, “If,…then,…formatted, “If,…then,…because….”because….”

How to construct a How to construct a GOOD hypothesisGOOD hypothesis

HypothesisHypothesis► Must be in IF-THEN-BECAUSE format!Must be in IF-THEN-BECAUSE format!► TESTABLETESTABLE

Independent VariableIndependent Variable::The condition studied. It is controlled by the The condition studied. It is controlled by the

experimenter.experimenter.ex. Waterex. Water

Dependent VariableDependent Variable:: The condition affected by the ind. The condition affected by the ind.

variable. It can’t be controlled by the variable. It can’t be controlled by the experimenter.experimenter.

ex. Plant Growth ex. Plant Growth ControlControl: :

The condition that is represented in a The condition that is represented in a normal situationnormal situation

Constructing your “If” Constructing your “If” StatementStatement

1. Start your sentence with the word 1. Start your sentence with the word “If”“If”

►2. Write down one of the variables2. Write down one of the variables►3. Connect statement with one of the 3. Connect statement with one of the

following:following: is related tois related to is affected byis affected by CausesCauses 4. Write down the other variable4. Write down the other variable

Constructing your “then” Constructing your “then” StatementStatement

► - Write the word “then” (following the “if” - Write the word “then” (following the “if” section)section)

► - Make a comment on the relationship - Make a comment on the relationship between those two variables.between those two variables.

► Ex. Ex. If section:If section:► If water is related to plant If water is related to plant

growth,growth,

► Ex. Ex. Then section:Then section:► then the more you water then the more you water

plants, the bigger they will grow.plants, the bigger they will grow.

Hypothesis ExercisesHypothesis Exercises

►Salt in soil may affect plant growth.Salt in soil may affect plant growth.►Plant growth may be affected by the Plant growth may be affected by the

color of the light.color of the light.►Bacterial growth may be affected by Bacterial growth may be affected by

temperature.temperature.►Ultra violet light may cause skin Ultra violet light may cause skin

cancer.cancer.►Temperature may cause leaves to Temperature may cause leaves to

change color.change color.

Test the HypothesisTest the Hypothesis

► Experiments test Experiments test your hypothesis.your hypothesis.

► The best The best experimental design experimental design is is “controlled.”“controlled.”

Controlled ExperimentationControlled Experimentation When designing the experiment, the researcher carefully controls as many variables as possible.

Variables - things that may be expected to change during the course of an experiment. Ex.: temperature, humidity, sunlight, etc.

Three types:

•Dependent variable – the one the investigator measures. Ex.: growth rate

•Independent – what the investigator deliberately changes during the experiment; factors that will directly affect the dependent variable. Ex.: amount or type of fertilizer, temperature, amount of water. ONLY ONE (1) independent variable can be tested at a time.

•Standardized (controlled) – factors that are kept equal for all groups. Ex.: If groups get different amounts of fertilizer, then the type of fertilizer must be the same for all groups.

How to Identify IV and DVHow to Identify IV and DVIndependentIndependent DependentDependent

CauseCause EffectEffect

BeforeBefore AfterAfter

InputInput OutputOutput

What you doWhat you do What happensWhat happens

ExamplesExamples

DependentDependent IndependentIndependentCell phone billCell phone bill Minutes usedMinutes used

How far you driveHow far you drive Amount of gas you haveAmount of gas you have

Your 9 weeks gradeYour 9 weeks grade Number of assignments turned Number of assignments turned inin

How much money you earnHow much money you earn Hours you workHours you work

Cost of a speeding ticketCost of a speeding ticket Miles over the speed limitMiles over the speed limit

Time it takes to drive Time it takes to drive somewheresomewhere

How fast you driveHow fast you drive

Result of a football gameResult of a football game Who scores more pointsWho scores more points

Total calories and fatTotal calories and fat Number of hamburgersNumber of hamburgers

Controlled ExperimentationControlled Experimentation

In most experiments there is a control group and experimental groups. The two groups are as similar as possible, but the treatment group is the one that experiences the variable that you’re studying.

Control Group – group in which the independent variable is either eliminated or set at a standard value. You MUST have a control group in order to be able to measure the effects of your independent variable upon the dependent variable.

Experimental Group(s) – groups which are being exposed to the independent variable.

Collect DataCollect Data

► The results of an The results of an experiment are experiment are called called “data.”“data.”

► Scientists use their Scientists use their five senses to five senses to collect data.collect data.

Collect DataCollect Data

► Scientists often use specialized equipment Scientists often use specialized equipment to help them collect their data.to help them collect their data.

Analyze DataAnalyze Data

► Now that you have Now that you have your data, you must your data, you must make sense of it.make sense of it.

► Scientists use:Scientists use: ChartsCharts TablesTables Graphs Graphs Equations Equations

Making a GraphMaking a Graph

► Often the goal of an experiment is to find Often the goal of an experiment is to find the relationship between two variables the relationship between two variables (pressure and volume, time and (pressure and volume, time and temperature, etc.). As one variable changes, temperature, etc.). As one variable changes, so does the other. Graphing is a useful way so does the other. Graphing is a useful way to visualize and describe these to visualize and describe these relationships. relationships.

► Use the computer. If drawn by hand, graphs must be neat and Use the computer. If drawn by hand, graphs must be neat and on graph paperon graph paper

► Usually, the x-axis is for the independent variable (manipulated) Usually, the x-axis is for the independent variable (manipulated) and the y-axis for the dependent variable (responding). and the y-axis for the dependent variable (responding).

► Decide on the limits of the graph (maximum and minimum Decide on the limits of the graph (maximum and minimum values). Make sure they are appropriate for the data series.values). Make sure they are appropriate for the data series.

► Select divisions on the axes which are easy to read and use the Select divisions on the axes which are easy to read and use the space efficiently.space efficiently.

► Grid lines should be shown on the graph. Grid lines should be shown on the graph.

► Label both axes with both quantity and units. Ex: Volume (mL)Label both axes with both quantity and units. Ex: Volume (mL)

► Choose the correct graph for the type of data you are Choose the correct graph for the type of data you are representing.representing.

► Title the graph in a descriptive manner. Title the graph in a descriptive manner.

Graphing Checklist

Pie ChartsPie Charts

In a pie chart, each category is represented by a slice of the pie. The area of the slice is proportional to the percentage of responses in the category.

Figure 1. Pie chart of iMac purchases illustrating frequencies of previous computer ownership.

•Pie charts are effective for displaying the relative frequencies of a small number of categories. They are not recommended, however, when you have a large number of categories. Pie charts can also be confusing when they are used to compare the outcomes of two different surveys or experiments.

•For small samples, its better to use the actual # instead of percentages.

Bar GraphsBar Graphs

► Bar charts can also be used to represent frequencies of Bar charts can also be used to represent frequencies of different categories. A bar chart of the iMac purchases is different categories. A bar chart of the iMac purchases is shown in Figure 2. Frequencies are shown on the Y axis and shown in Figure 2. Frequencies are shown on the Y axis and the type of computer previously owned is shown on the X the type of computer previously owned is shown on the X

axis.axis.

Figure 2. Bar chart of iMac purchases as a function of previous computer ownership.

Line GraphsLine Graphs

►Usually measures frequency over a Usually measures frequency over a span of time.span of time.

►X-axis is always the length of time and X-axis is always the length of time and Y-axis is the frequency.Y-axis is the frequency.

What does the data mean?What does the data mean?

There are two options:There are two options:

► The evidence The evidence supports the supports the hypothesis.hypothesis.

► The evidence is The evidence is inconsistent with the inconsistent with the hypothesis.hypothesis.

What do you do?What do you do?

If the data is inconsistent with the If the data is inconsistent with the hypothesis, hypothesis, youyou revise your hypothesisrevise your hypothesis in in light of your new information. Then you light of your new information. Then you design a new experiment.design a new experiment.

OK, I’ve got it all right. Now OK, I’ve got it all right. Now what?what?

Tell everyone, Tell everyone, silly!silly!

Scientists publish Scientists publish their findings to their findings to share what they’ve share what they’ve discovered with discovered with other scientists other scientists (and to brag a (and to brag a little, too.)little, too.)

What do you do?What do you do?

If the data supports the hypothesis, you If the data supports the hypothesis, you repeat therepeat the experiment several timesexperiment several times to to make sure you did everything right.make sure you did everything right.

SummarySummary