Activity 4: Experiment (YOU PRETEND TO DO THISEXPERIMENT)

The control group in an experiment is the groupwho does not receive any treatment and is used as a benchmarkagainst which other test results are measured. A control group isused in an experiment as a point of comparison, so that it can beisolated in testing that the experiment did, or did not, have theintended effect.

For example, scientists have developed many tests using reagents(substances used to detect another substance) to identify thedifferent biomolecules. In order to perform these tests correctly,two different treatments must be completed to provide standards forcomparison. The first treatment is called a positive control andcontains the variable being tested for. The second treatment is thenegative control, which does not contain the variable being testedfor. To make sure your testing chemicals are not contaminated andto see what a negative reaction to the test will look like.

• Exercise 3: Identify the parts of the experiment.  A researcher wants to find out if spraying fruitsand vegetables with pesticides affects the vitamin levels in thosefoods.

     a) the independent variable:_______________________________________

     b) the dependent variable:_____________________________________

     c) two possible controlled variables:________________________________

     d) the control group:  ___________________________________________

     e) the experimental group:__________________________________________

Activity 5: Data

Data are reported in objective terms that allow for independentinterpretation by anyone reading the report. The preferred methodof reporting data is the presentation of results in tables andgraphs that provide a quick and clear overview of any observedeffects. There are two types of data: qualitative andquantitative.    

Qulitative data include qualities such ascolor, smell and taste. These are subjectively perceived and can bedifficult to express in an objective manner. While everyoneconducting the experiment may agree that the solution changedcolor, there may be variation in what individuals identify as blue,light blue, etc.

Quntitative data include qualities that can bemeasured objectively such as weight, volume, length andtemperature. Quantitative data have a number associated with themand can be reported in universally accepted measurable units. Thismakes it easy for others to interpret the results. Both types ofdata are valid and important. In some instances an experiment mayresult in just one or the other type of information. Frequently,the investigator may collect and report both types of data.

Exercise 4: Label the following as qualitative (L) orquantitative (N).

Temperature of 23 °C _____

Increase in color intensity _____

pH values _____

Bitter taste _____

Sound increase _____

Measurement of nitrates _____

Number of deaths _____

Precipitation _____

Sweet smell _____

Level of diversity _____

Activity 6: Results/Analysis

To understand data better, it is usually shown in some type ofgraphical format. The same data can be portrayed in differentformats depending upon what is being emphasized. A pie chart showsthe proportions of different categories (qualitative data). Theamount of the pie (circle) correlates to the percentage. It can beas simple as just two categories or it can contain severalcategories. The more categories a chart has the more difficult itis to read. If there are many categories that have small numbersthey are frequently lumped into an “Other” category.

Exercise 5a:   Creating a complexpie chart. Create a pie chart for a characteristic with at leastfour categories but not more than six. Choose a characteristic thatvaries among students. Appropriate examples include shoe type,color of pants, mobile phone service, or type of car owned. Eachstudent should pick a different characteristic. To make datacollection easy and fun, one by one students should introducethemselves to the entire class and the rest of the class can askthem about the characteristic they chose. Fill in the chart belowand create a pie chart with your data.  

Characteristic _______________________

Category	Number of Students	Percent of Students
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