The Data Collection and Statistical Analysis in IB Biology John Gasparini The Munich International School Part I – Introduction and Uncertainty in Measurement

Introduction: This set of presentations is meant to serve as an auto-tutorial introduction to the way in which data must be reported and processed in your IB Lab work. Try your best to understand what is presented, but if you have questions about anything covered, please write them down in your notebooks so that I can help you in class with an explanation.

Introduction continued… The way in which you report, process and analyze data is going to have to change dramatically from what you were used to doing in grades 9 and 10. Don’t worry, though. We’ll go through this material slowly and thoroughly until you are confident in these new skills.

Part I - Intro and Uncertainty in Measurement Part II - Mean, Mode, Median, Standard Deviation and Variability Part III -How to Use Excel to Process and Present Data Part IV -T-tests and Chi-Squared Tests of Significance Part V -Linear Regression and Correlation Part VI - Stats Test Flowchart! Topics Covered

Throughout these presentations we will practice certain skills by analyzing entomological data (bugs)… We are going to see if there exits statistically significant differences in the biologies and behaviors of different insects. …and we will try to address a simple research question.

feeding-on-yellow-flower-art-skopec-state-f-the-art-photography.jpg Most butterflies and moths are nectarivores, meaning they feed on the sugar-rich nectar of flowers. In return for food, they act as important pollinators for many plant species. This is an example of MUTUALISM We’ll focus on Lepidoptera.

Butterflies and moths have an interesting way of feeding. One of the more defining characteristics of lepidopterans is their straw-like proboscis. It is held coiled under the head when not in use. During feeding, however, it is extended to reach the nectar of flowers. Proboscis coiled Proboscis uncoiled during feeding

Researchers studying the evolution and ecology of Lepidoptera often take measurements of the proboscis length and body mass of these insects for comparative purposes. The treatment of data collected in scientific investigations is known as STATISTICAL ANALYSIS

ZeMas/TWWe7aOgiWI/AAAAAAAAAP8/ck9cmUdqfas/s1600/Adelpha _cytherea_ButterflyPhotography-BB_Blogspot_JGJ.jpg Let’s start simply…lets compare two species of butterflies: Smooth-Banded Sister (Adelpha cytherea) Spot Celled Sister (Adelpha basiloides) These are closely related species from the Nymphalidae family - both are found in the tropics of Central America and both feed on the nectar of flowers. "Is there a significant difference in proboscis length and body mass between A. basiloides and A. cytherea?” Research Question

Important things to consider as any researcher begins a study: Sample Size – must be big enough to generate reliable data Uncertainty – what are the uncertainties associated with the measurements to be taken? (There are many, many other things to consider, but we will focus on these for now! ) Channel your inner nerd.

1) Sample Size There is a great deal of science and statistics behind determining the appropriate sample and sample size for a study, but be aware, for the sake of your IB lab designs… The IB expects a minimum of 5 SAMPLES or 5 REPEATS for each independent variable value! (This may be impossible because of time constraints, but make sure to include sufficient repeats (5x) in your lab protocol. We’ll talk more about this later.)

2) Uncertainly in Experimental Measurements All measurements have a degree of uncertainty regardless of precision and accuracy. This is caused by two factors: the limitation of the measuring instrument (systematic error) the skill of the experimenter making the measurements (random error). UNCERTAINTIES MUST BE RECORDED AND REPORTED WHEN YOU PRESENT YOUR DATA IN ALL OF YOUR LAB WRITE UPS!

2) Uncertainly in Experimental Measurements How do you determine the uncertainties in taking measurements? It depends on the type of measuring instrument that is being used! ANALOG vs. DIGITAL DEVICES Uses continuous range of values to represent information measured Uses discrete or discontinuous values to represent information measured

ANALOG vs. DIGITAL DEVICES Spectrophotometers Thermometer Balances

UNCERTAINTY USING DIGITAL DEVICES How do you determine the margin of error in taking DIGITAL measurements? Here we have an avocado… for some reason we want to know its mass and the uncertainty in this measurement g (+/- 0.1g) For a digital device the uncertainty is equal to the smallest division on the display. Uncertainty This balance reports to the nearest 1/10 th of a gram.

What is the uncertainty in the digital mass measurement of this butterfly? +/- what value?

What is the uncertainty in the digital mass measurement of this butterfly? Answer: (+/ g) Reports to the nearest 10,000 of a gram. Record reading as: (+/ g)

UNCERTAINTY USING ANALOG DEVICES How do you determine the margin of error in taking ANALOG measurements? Here we have a triple beam balance…try your best to determine the proper reading and its uncertainty g (+/- ???) For an analogue device the uncertainty is equal to +/- one half of the smallest MEASURED division on the display. (measured/2 = uncertainty) This analog balance reports to the nearest 1/10 th of a gram but this is an ESTMATED READING. ESTIMATED MEASURED

UNCERTAINTY USING ANALOG DEVICES How do you determine the margin of error in taking ANALOG measurements? Here we have a triple beam balance…try your best to determine the proper reading and its uncertainty g (+/- 0.5g) For an analogue device the uncertainty is equal to +/- one half of the smallest MEASURED division on the display. (1 gram/2 = 0.5 g) Uncertainty This analog balance reports to the nearest 1/10 th of a gram but this is an ESTMATED READING. ESTIMATED MEASURED

What are the readings and uncertainties on these thermometers? ANALOG OR DIGITAL? READING AND UNCERTAINTY? 1) 2) 3)

What are the readings and uncertainties on these thermometers? ANALOG DIGITAL -8.5 °C (+/- 0.1 °C) °C (+/-0.5 °C) 1) 2) 3) -9.0 °C (+/-0.5 °C)

RULERS AND METER STICKS ARE A BIT TRICKY IN THEIR UNCERTAINTIES! Where does this moth’s proboscis begin and end? ? ? UNCERTAINTY EXISTS AT BOTH END OF THIS RULER!

RULERS AND METER STICKS ARE A BIT TRICKY IN THEIR UNCERTAINTIES! Lets say that this blue line below represents the proboscis fully extended… (+/- 0.5 mm) Combine the uncertainties at both the beginning and end of the ruler. Proboscis (+/- 0.5 mm) + Reading = 4.4 mm (+/- 1.0 mm)

Provide a measurement for this butterflies wingspan. Be sure to include the uncertainty in your measurement.

What is the pH of this solution? Provide the reading and the uncertainty. What is the mass of this beetle? Provide the reading and the uncertainty.

What is the diameter of this larva’s head? Provide the reading and the uncertainty.