1 Scientific MethodNames of contributing authors:_______________________________________________________________________State contributions of authors:_________________________________________________________________________BackgroundThe scientific method refers to a set of techniques for investigating natural phenomena. It involves observing natural phenomenon and asking a question. Next comes making a hypothesis (tentative answer), and predictions based on the hypothesis. Then comes carrying out experiments to test those predictions to determine whether or not the original hypothesis is correct. If conducted properly, knowledge acquired from these investigations provides our most reliable understanding of nature. Observations and questions asked at the start of any scientific investigation are based on curiosity of personal observations or derived from unexplained data from previous studies. While common questions refer to explanations of specific observations such as “Why can birds fly but we cannot?”, the scientific method can also include questions as open-ended as “Can we find a cure for all types of cancer?” or even those that aim to reconstruct past events like “What happened in this ancient site a million years ago?”. Let’s follow an example study to help illustrate the scientific method. An investigator observed that patients with a particular cancer tended to also have a high intake of artificial sweetener. She then questioned “Is there a link between artificial sweeteners and cancer?” Hypotheses are then formulated based on previous knowledge or experiences about the natural phenomenon. The hypothesis aims to explain the observations and questions in a testable way. To be scientifically useful, however, it has to be falsifiable. This means that one can envision an experimental result that conflicts with predictions derived from the hypothesis; otherwise, it cannot be meaningfully tested. In our example study, the investigator hypothesized that artificial sweeteners increased the risk for cancer. Predictions are logical consequences of the hypothesis. They state what the outcome should be if the hypothesis is true. One or more of them could be derived from the same hypothesis. The more specific and measurable they are, the more easily they can be tested. In our example study, the prediction is that more rats that were fed sweeteners would develop cancer compared to the rats not fed sweeteners. Usually the hypothesis is written as the “if” statement and is followed by the prediction which is the “then” statement. For example, if artificial sweeteners increased the risk for cancer, then more rats that were fed sweeteners would develop cancer compared to the rats not fed sweeteners. Experiments, or hypothesis-testing, are the next step that investigates whether the real world behaves as predicted by the hypothesis. If observations of the real world agree with the predictions, confidence in the hypothesis increases; otherwise, it decreases. Note that agreement does not assure that the hypothesis is true because future experiments may reveal different results. Knowledge in science is never absolute. They are as good as the most recent evidence. The most reliable way to test hypotheses is by conducting experiments that minimize potential errors, preferably through the use of appropriate control groups. A control group is a group that is not exposed to the variable being tested. It serves as a comparison to the experimental group which is exposed to the variable being tested. Any difference in outcome between the two groups is due to the variable being tested. In this experiment, the independent variable is the one being tested. The outcome, or what is being measured, is the dependent variable.In our example study, 100 rats were tested. All conditions were the same except that the investigator fed 50 rats with the sweeteners (experimental group) and 50 rats without sweetener (control group). The independent variable is the amount of sweetener. The dependent variable is the number of rats that got cancer. In this case, 15 rats in the experimental group got cancer. Two rats in the control group got cancer. Do our results support our hypothesis and prediction? If artificial sweeteners increased the risk for cancer, then more rats that were fed sweeteners would develop cancer compared to the rats not fed sweeteners. Yes, our results match the prediction therefore we support the hypothesis. Results include the data that are the facts or values collected from the experiment. In the rat cancer study, the results are the numbers of rats with and without cancer for each group. Discussion and Conclusions are interpretations made based on the results. When discussing the data, scientists compare the actual results to the original prediction that is based on the hypothesis. If the results and prediction match, then the hypothesis is supported. Otherwise, the hypothesis is rejected, and needs to be revised. The conclusion can address the applications and greater importance of the study. In the above study, the discussion addresses that the hypothesis that artificial sweeteners increased the risk of cancer was supported. In conclusion, these findings are important because it suggests that one might choose to not intake as much artificial sweeteners. Review: This video reviews the steps of the Scientific Method discussed here and the overall process of science. Scientific method by the Amoeba Sisters (9 min 51 sec)Purpose Review the steps of the scientific method Analyze a case study that used the scientific method Materials Case study: The Strange Case of Beriberi Procedure Read the case study. Answer the questions. The Strange Case of BeriberiIn the late 1800s, several diseases were known to be caused by bacteria. In 1887, a strange nerve disease called beriberi attacked people in the Dutch East Indies. Symptoms included weakness and loss of appetite. Victims often died of heart failure. Scientists hypothesized that beriberi might also be caused by bacteria infecting the blood. To test this hypothesis, they injected one group of chickens with bacteria from the blood of patients with beriberi. These injected chickens became sick with beriberi. However, another group of chickens that were not injected with the bacteria also became sick with beriberi. Dr. Eijkman noticed that the chickens had eaten whole-grain rice before the experiment began, but they were fed polished-grain rice during the experiment. He discovered that polished rice lacked a vitamin called thiamine. Discussion/ConclusionPlease answer the questions below:What was the observation and question asked that led to this investigation?What was the hypothesis and prediction? Briefly describe the experiment that the scientists performed to test the hypothesis and prediction. What were the independent and dependent variables? Describe the experimental group. Describe the control group. What were the results? Explain why the hypothesis can not be supported by the experimental results. Write an alternative hypothesis that may explain these experimental results. Describe an experiment to test this new hypothesis.Further review and exploration of the process of science:Scientific theory versus lawThese videos explain the difference between a theory and a law.Theory vs. law: What’s the difference? TedEd article and video (5 min 11 sec)Scientific theory & law by Amoeba Sisters (5 min)Nature of ScienceThis video discusses the process of science.Nature of Science (3 min 2 sec)Experimental DesignThis video discusses and gives several examples of experiments focusing on variables.Biology: Independent and dependent variables (3 min 16 sec)2 MetricsNames of contributing authors:_______________________________________________________________________State contributions of authors:_________________________________________________________________________BackgroundIn the United States our measurements are usually based on the imperial system from Great Britain. This British system of measurements which includes units such as feet, pounds and gallons has deep historical roots. For example, the foot is thought to be the length of the foot of King Henry I of England in the 12th century whereas the pound is based on the Roman word libra (lb) which is the equivalent to the weight of 7,000 grains. Scientists, however, decided to adopt a different measurement system because of its tremendous advantages. The metric system (see table 1), the most commonly usedstandardized system worldwide, not only covers a large scale and its measurements are also in consistent units of 10 (see table 2) which makes calculations simpler.Since many people in the United States are used to the imperial system, we must become familiar with the metric system. Often we need to convert between the two systems. Below are some helpful conversions.Conversions Between Imperial and Metric Systems1 kg = 2.2 pounds1 km = 0.62 miles1 m = 39.37 inches1 inch = 2.54 cm1 l = 1.06 quartsThe following activity will help you review the scientific method as well as work with the metric system. To learn more about the history of how the metric system was implemented, you can watch this video: Why the metric system matters by TedEd (5 min 11 sec) Title:__________________________________________________________________________(Note: At the end of the experiment, you will create a title.)Background Observation and question: People have observed that a person with a longer upper or lower limb tends to be taller. We then asked the question: “Is the length of a person's upper limb directly proportional to his/her height?” Two measurements (variables) are directly proportional if, for example, as one amount increases, the other amount increases at the same rate. The upper limb spans from the armpit to the end of the fingertip. Hypothesis and prediction: If the length of a person's upper limb is directly proportional to height, then the ratio of upper limb length to height for all subjects must be constant, i.e., the same.PurposeUse the metric systemReview steps of the scientific methodMaterials Measuring tape/tool or meter stick or measuring app on phone: Ruler for Android, Measure App on Apple or piece of paper (8.5 x 11) to use as a measuring device 3-4 human subjects 1 calculatorProcedurePick 3-4 subjects from group members.Each subject puts right arm straight out (parallel to the ground).Using the meter stick or measuring tape/tool, measure upper limb length (from arm pit to the end of the finger tip) of subject 1 in cm.Record measurement in Table 1 below.If subject 1 does not know height, then measure height in inches and cm.Practice converting height in inches to cm. Show work below.Record height of subject 1 in cm in Table 1 below.Calculate ratio of upper limb to height of subject 1 and record in Table 1.Repeat measurements and calculations for all subjects and record in Table 1.Results:Table 1. Comparison of Limb Length to Height in Group SubjectsSubjectMeasured Upper Limb Length (cm)Height* (cm)Ratio of Upper Limb Length to Height = Upper Limb Length (cm)/Height (cm)1.2.3.4.* 1 inch = 2.54 centimetersSubject 1, 2, 3 and 4 had a ratio of upper limb length to height of_____, _____ , _____ and ____ respectively. Average of group subjects' ratio of upper limb length to height was __________.Average of all class subjects’ ratio of upper limb length to height was _________.Discussion/Conclusion (~1 sentence each): Do your results support or reject the original hypothesis? Explain your answer.Based on an analysis of your data and the class data, what conclusions can you make?Describe one future experiment you would like to do to extend or make these findings more reliable.Metric System Practice Problems (Optional) Note: For metric system, know how to convert within the metric system (ie. meters to mm, mg to grams). Also, know how to convert between the metric and imperial system.A pen is approximately 12 (µm mm cm m). Circle one.A chair is approximately 2 (nm cm m km) high. Circle one.Convert the value on the left into the unit indicated on the right of the equation below. Show work.2,346 m = ____ km5 ft, 9 in = _____ cm (1 inch = 2.54 cm)6 km = _____ miles (1 km = 0.62 miles)208 mL = ____ L2.67 kg = _____ g80 nm = ______ mJoe weighs 152 pounds. What is his weight in kg? Show work. (1 kg = 2.2 pounds)Mary’s height is 175 cm. Mark’s height is 5 ft 6 in. Who is taller?Explain and show work. (1 inch = 2.54 cm)(Hint: convert Mary’s height into inches, OR convert Mark’s height into cm)