Methods of Science (Holt)
Principle(s) Investigated: making and testing hypotheses, collecting data and analyzing data, expressing data graphically
Standards : 1. Investigation and Experimentation
a. Select and use appropriate tools and technology (such as computer-linked probes, spreadsheets, and graphing calculators) to perform tests, collect data, analyze relationships, and display data.
b. Identify and communicate sources of unavoidable experimental error.
d. Formulate explanations by using logic and evidence.
e. Distinguish between hypothesis and theory as scientific terms.
g. Recognize the usefulness and limitations of models and theories as scientific representations of reality.
j. Recognize the issues of statistical variability and the need for controlled tests.
k. Recognize the cumulative nature of scientific evidence.
l. Analyze situations and solve problems that require combining and applying concepts from more than one area of science.
Materials: 20 pieces of common string 50cm in length or 20 flexible measuring tapes
(the type used for sewing)
1 meter stick per pair (sticks not needed if using measuring tape)
2 meter length of masking tape with marks indicating length every 5 cm
Procedure: Students will be testing a hypothesis they have created. The question posed is “Does head size (measured by circumference) predict long jump distance?
Students will work in pairs and perform two measurements.
1. The first one is to measure their partners head circumference by wrapping a string around their head (level with the ground, just above the eye brows see image below) and then measuring the length of string with a meter stick . This is to be done 3 times, and the average length recorded. The pair will be finished when each partner has completed measuring the others head size.
2. The second measurement is the standing long jump. One partner will jump while the other watches where the back of the heel lands and records the distance. This also is done three times and the average computed and recorded.
3. Measurement is made easier by placing a two meter length of masking tape on the floor, pre-marked in 5 cm increments. If this is placed in the middle of the jumping area, students can use both sides of the tape and jumping can be completed in a timely manner.
4. After initial “how to” demonstrations are made students can be broken down into two groups.
One groups measures heads first and the other jumps. Groups then switch.
5. When completed, students record their data on the white board (in a traditional classroom) or on device in an ”online” classroom.
6. In a traditional classroom students will then record the classroom data on a data table. Then they will graph the 30 or so pairs of numbers. Head size is the X axis and the jumping data is the Y axis.
I share the D over T logo to help them remember which axis to use for what data.
7. Once data is plotted in a scatter graph then you may ask what does the data show? The data should not show a correlation and the points should be spread out without a pattern. Sometimes it will take a few minuets for them to say there is no connection, they want to find something. Eventually someone says something to the effect that the experiment is a failure. This is a great opportunity to talk about the fact that all experiments produce knowledge, and that finding no correlation is as valuable as finding a correlation.
Student prior knowledge: Students need to know basic measuring, graphing and experimentation.
Explanation: This activity gives students a chance to create real data, analyze that data in one class period. With younger students (9th grade) the discussion prior to the activity really provides a valuable learning experience. They have all used data they have produced in prior science classes, but most of this is considered “boring,” mostly just dry numbers reflecting changes in temperature or something equally mundane (in their opinion.). This activity is all about their favorite subject, themselves! The other thing that really makes this work is that you are able to teach pure science method without complicated science “content” getting in the way. Freshman and unsuccessful sophomores traditionally have difficulty with dependent and independent variables. This is a great way to introduce that concept and gives you something memorable to refer back to all year long. i.e. “Remember when we did the head size experiment, the dependent variable was ….”
.
Questions & Answers:
1. When your partner measured your head and jumping what were some potential sources of error?
Potential sources of error should include stretching of the string, placing the string in a different place each time and fingers slipping on the head. These sources of error should be extended to the jumping section, tape could be marked incorrectly, observation of landing spot wrong and falling when landing. Discussion should include topic of unavoidable error and averaging technique used to minimize error.
2. If head size is related to jumping ability what pattern should we expect to see in the graph?
I start this discussion with question of “What is graph really showing?” Class should end up with the further down the the X axis the higher up the Y axis if head size correlates with jumping ability. So if the head size is related to jumping length then a slope pattern should develop.
3. Do you think the results would be different if we tested every student at this school?
Results should not be much different than the class. If anything they should further confirm that there is no correlation between head size and jumping.
4. Predict what would happen if conducted this same experiment with 100 kids aged 3 - 10.
Hopefully the prediction will change and if the sample was this young then growth and coordination (and therefore jumping ability has a greater chance of correlating with head size
Applications to Everyday Life:
Mechanic- What must he change in the car to repair it?
Business Owner- Do my sales increase if I advertise on the radio? or television?
Police- Does the speed of cars involved in an accident increase the number of injuries?
Student- If I study more hours do my grades improve?
Photographs: Coming soon!