Now you know what a hypothesis is, and you also know that daddy-long-legs are not poisonous.

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1 Objectives: Be able to explain the basic process of scientific inquiry. Be able to explain the power and limitations of scientific inquiry. Be able to distinguish a robust hypothesis from a weak or untestable hypothesis. Learning outcomes 1. Understand the difference between a hypothesis and a theory. 2. Develop scientific hypotheses. 3. Distinguish between good and bad hypotheses. 4. Understand the importance of testability and falsifiability in scientific hypotheses. Developing a hypothesis Science advances by testing hypotheses. A hypothesis is a tentative answer to a well framed question. For example, imagine that an arachnologist is tired of hearing people say that daddy-long-legs are the most poisonous animals in the world, but their fangs are too small to pierce human skin, and thus they are harmless to humans. To see if this is true, the arachnologist would start with the question Are Opiliones poisonous? (Opiliones is the taxonomic name for daddy-long-legs; and the word Opiliones denotes both the singular and the plural). From this, he could make the hypothesis: Opiliones are poisonous. As you can see, the hypothesis is not framed as a question, but rather as a tentative answer to the question. Note that in this particular example, the hypothesis is very similar to the original question., but this not always the case, since questions tend to be general, and good hypotheses tend to be very specific. But for this explanation, we'll take these questions and hypothesis. So, from the current hypothesis Opiliones are poisonous, the arachnologist could then make a prediction: If Opiliones are poisonous, then I will see poison glands when I look at one under the microscope. This hypothesis is both easy to test, and easy to prove wrong if in fact it is wrong (but see below about the verb to prove ). To test it, the arachnologist would just have to put a species of Opiliones under the microscope and look for poison glands. And if he does not find poison glands, that will falsify the hypothesis. So he puts an Opiliones under his microscope, and does not see any poison glands, and with this, he can say that the hypothesis is false, or rather, that it has been falsified. Note that scientists prefer to say that a hypothesis was either falsified or that they failed to falsify the hypothesis. This is similar to what the people mean when they say that they proved or disproved something. However, because of philosophical issues that are beyond the scope of this lab, there are no absolute proofs in science, and thus, the term to prove something is not generally used in scientific writing. Now you know what a hypothesis is, and you also know that daddy-long-legs are not poisonous. A hypothesis is the product of deductive reasoning, going from general premises to the specific results one would expect if those general premises are indeed true. The process of testing hypotheses is used throughout science: from field ecologists to computer scientists to astronomers. Please also note that the word theory is used by the public to mean that something is just a thought experiment, as in theoretical. However, in science the word theory is reserved for whole bodies of knowledge, backed by hard facts (that is, data), and which have predictive properties. For example,

2 gravitational theory can be used to predict that if you drop something from a table, it will hit the ground, or to predict the speed of rotation of a planet around the sun. Evolutionary theory, on which the whole field of biology is based, is also a theory in the same sense that gravity and thermodynamics are. When nonscientists say things like I have a theory that eating too many carbs is what makes people gain weight, not eating fat, what they mean is that they have a hypothesis that carbs are the cause of weight gain. This hypothesis is both testable and falsifiable. But it's not theory. How to develop hypotheses. The process of developing and testing hypotheses is very similar to what a car mechanic does when attempting to fix a car. For example, imagine that your car does not start in the morning, so you take it to the mechanic. To fix the car, the mechanic would start with the initial observation: the car does not start. After this observation, the obvious question would be "Why is the car not starting?" Then comes the interesting part, when the mechanic comes up with tentative answers or hypotheses. For example: 1. The car does not start because the battery is dead. 2. The car won't start because the starter motor is damaged. 3. The car won t start because it is out of gas. 4. Etc. Please note again that the hypotheses are framed as statements or tentative answers to the questions. The mechanic could come up with many more hypotheses, as scientists often do, but for now let's leave it at the ones listed above. These tentative answers are perfectly good scientific hypotheses because they are: Testable All of these hypotheses can be tested: the battery can be changed, the starter motor replaced, and gas can be put in the car. Falsifiable If the mechanic were to change the battery but the car still not start, then the first hypothesis would be falsified. If the mechanic then changes the starter motor, and the car still does not start, the the second hypothesis would also be falsified. And so on. Not all hypotheses are scientific Please note that just because anybody can make a hypothesis, this does not mean that all hypotheses are scientific. For example, if the mechanic were to say the car does not start because it is possessed by an invisible, undetectable, unmeasurable ghost, that would not be a good scientific hypothesis. It would not be scientific because there is no way for a mechanic to test for the presence or absence, never mind the effects of, something that has no physical or natural properties. This can get complicated. For example, if the mechanic were to hypothesize that praying to the car would make it start, that would be a falsifiable hypothesis: he would just have to pray to the car, and test if it starts. The key to identifying bad hypotheses is thus not in crossing out the possibility of unknown forces, but in crossing out hypotheses that cannot be tested or falsified.

3 In today's laboratory exercise, you will be given two boxes, one sealed and with several objects inside, and one empty box with several objects beside it. You have to try asses what are the objects inside the sealed box by developing testable, falsifiable hypotheses and testing them. At the end of the lab, you will be able to open the sealed box and see if your conclusions about the contents were accurate. As you go through the lab, please note that the professor will not evaluate if your hypotheses were falsified or not, in other words, there will be no points off if you are wrong about what was inside of the box. All of the points will be awarded for (1) developing a set of hypotheses that are both testable and falsifiable, and (2) writing a lab report that follows the instructions in this lab. WORK IN GROUPS of 3-4 students. 1. WRITE DOWN all measurements and other observations. 2. Also write down all hypotheses that you test, all tests that you conduct, and all outcomes. 3. When your group reaches agreement as to the contents of the sealed box, WRITE DOWN your prediction in the form of a hypothesis. 4. Test your hypothesis by opening the box. (This type of test is possible only for hypotheses about very specific occurrences, such as "my lab on this day"; tests of this kind are not usually possible for the widely applicable hypotheses that scientists usually consider.) 5. IN YOUR WRITE-UP, discuss your outcome. If you guessed correctly, explain how you arrived at your hypothesis and how you tested it. If you guessed incorrectly, explain what led you astray and how you might have avoided being led astray in this way. INSTRUCTIONS FOR WRITE-UPS are on the LAST PAGE. Here is an example of how a group of students might go about developing good hypotheses for the content of the box: 1. Question: What is inside the box? 2. Hypothesis 1: There is something made out of metal inside the box. 3. Prediction: If I drag a magnet through the outside of the box, I should feel a pull of something metal inside. 4. Test of Hypothesis 1: Drag the magnet around the box.

4 5. Observations (data collecting): The magnet was attracted (or was not attracted) to something metal inside the box. 6. Conclusions for the test: If you felt a magnetic pull: you conclude that there is probably something metal inside of the box. If you did not feel anything: there's probably nothing made out of metal inside of the box. In your lab, go through the steps above for testing the hypothesis that there is something metal inside of the box. After recording your data, develop a few more hypotheses and go through a few more rounds of hypothesis prediction test observations conclusions. Sometimes students start by weighting the closed box, and then putting different combinations of objects inside of the open box until the weight matches. This procedure is still a way of testing hypotheses, which could be framed, as for example: The closed box has a cuvette and a sponge inside. Whatever hypotheses you develop and decide to test, just make sure that they are both testable and falsifiable. Also, make sure to keep records of all your hypotheses and tests, as you will need these to write your report. After reaching your conclusions about what is inside of the box, you will have the opportunity to do what no scientist gets to do: lift the lid on the universe and know the truth. It is important to note that opening the black box is not part of testing any of the hypotheses. If your tests led you to the wrong conclusion, i.e. you were wrong about the contents of the box, there are several possibilities, all which are very interesting from the perspective of philosophy of science: 1. You did not test enough hypotheses. Scientists working to understand our natural universe do not get to open the universe up and check their answers, so they never really know when they have tested enough hypotheses and reached the correct answer. 2. Your measurements were wrong. This is why scientist put so much attention into using precise instruments when collecting their data. 3. Differences between the closed box and its contents, and the empty box and objects you were provided (your sample, in the jargon of a scientist). Differences in production of the boxes, variations in the cardboard material, etc. can cause different boxes to be of slightly different weights. Same thing for the cuvettes, microcentrifuge tubes, and other objects. This is why scientist insist in doing multiple measurements of the same phenomena, to try assess what is the natural existing variation. For example, if you had had the opportunity to weight 30 different boxes, that would have given you an idea of how much variance, or differences, you could expect among the boxes, and adjust your expectations accordingly. A useful measure of this variance, or differences, is called the standard deviation. This statistical term is outside of the scope of this lab, but you will see it again when you take more advanced classes. Vocabulary These are terms whose meaning you should know. 1. science 2. hypothesis 3. theory 4. prediction 5. test 6. experiment 7. falsifiability 8. testability Thought questions: 1. What is the difference between a hypothesis and a theory? 2. What is the difference between a hypothesis and a test? 3. What does it mean that a good hypothesis must be falsifiable? 4. What does it mean that a good hypothesis must be testable? 5. Can science address questions of supernatural phenomena? Why or why not?

5 Black Box Write-up Instructions For this lab homework, you need to write a brief (no more than 2 pages) report that answers the following questions, either in paragraph form or in a numbered list: 1) What was the process your group used to determine what was inside the box? What kinds of observations did you make? What hypotheses did you develop? How did you test these hypotheses? Did you consider the possibility that the box contained more (or fewer) objects than you had been told, and how might this uncertainty have affected your hypothesis? 2) When you opened the box and discovered the truth, did it match your hypothesis about the contents of the box? Was your hypotheses verified or falsified? Can a hypothesis about one box be verified? Can most scientific hypotheses? Why or why not? 3) What could have led you astray, or made it difficult to test your hypotheses? What sources of error may have been present? Were there elements of luck involved? 4) Is it possible that your box contained a weightless, invisible ghost or spirit in addition to the physical objects? Discuss whether this is a hypothesis worth considering, and why. (NOTE: "I don't believe in spirits" or "Ghosts don't exist" are not suitable answers because they do not address these questions for skeptical readers. Ask yourself whether you can tell the difference between a marble+glove+ pipette and a marble+glove+pipette+ghost, assuming that the ghost is weightless and invisible.) 5) If your guess was wrong, is it possible that you were really correct, but an evil spirit changed or switched the objects in the split-second before you opened the box, just to make you look bad? If your guess was correct, is it possible that you were really wrong, but a kindly spirit changed or switched the objects in the split-second before you opened the box, just to make you look good? Discuss whether these possibilities are hypotheses worth considering, and why. Your grade for this laboratory will be based on how well you answer these questions, not on how close you were to figuring out what was inside the closed box. The key to a good grade is to demonstrate that you developed hypotheses that were testable and falsifiable, and tested them, and understood the scientific nature of the process you were following. YOU DO NOT NEED A COMPLETE EXPERIMENTAL WRITE-UP; JUST ANSWER THE FIVE QUESTIONS LISTED ABOVE. The due date for this assignment is one week (seven days) after you complete the lab. You may submit your write-up either on paper (handed in during class or lab) or electronically. Electronic submissions should be in either.doc or.pdf format, attached to an and sent no later than 11:30 p.m. on the due date. Please do not submit your report using Google Docs or any similar software! These same rules also apply to all other written assignments in this course.

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