Scientific Method Make Up.
Use the data at the end of the exercise.
In this lab, we will be applying some of what we’ve learned about the scientific method. Let’s imagine that we have a crime scene and at that crime scene we have footprints. We’d like to find the person who made them and part of the description of that person is how tall they are. So, the question is, can we figure out how tall someone is based on how big their footprint is? The answer is yes but how?
To begin with, consider that you’re in a room with 20 or so other people all of whom have a height and a foot size. There’s your data. So the first step in our process is data collection you want to use a meter stick to measure the height and foot size (with their shoes on) of a partner then have your partner measure you.
A few words about the metric system. The stick you’re holding is a meter stick. A meter is divided into 10 decimeters and a decimeter is divided into 10 centimeters and a centimeter is divided into 10 millimeters (those are the smallest divisions on your meter stick). Your partner’s height in meters will be between 1 and 2 meters. The first digit after the decimal is decimeters and the second is centimeters there is no need to measure them down to the millimeter. So, if they’re 1.78 meters tall 1 meter 7 decimeters, and 8 centimeters. Their foot size will be between 20 and 30 centimeters and here you can measure to the millimeter so 25.6 is 25 centimeters and 6 millimeters. Throughout the semester we’ll be using the metric system.
1) Measure the height in meters and the foot size in centimeters of your partner then have them measure you.
2) Once you have these measurements come to the front of the class and write them on the board, so everyone has all the data.
Now, what do we do with these data? Our first impulse may be to just average them and come up with some sort of a ratio. But that takes 20 data points and turns them into one with no idea how good that one data point is. There are times to average data, this is not one of them. Instead, what we want to do is graph them.
3) Graph your data, put the foot size on the x-axis and the height on the y-axis. Keep in mind there is no rule that says the origin of the graph needs to be 0,0 you want to scale your x and y axis to get the best look at your data.
Now we want a line, we want one straight line that goes through the center of all our data Don’t connect the dots. draw one straight line so that half your points are above, and half your points are below that line.
4) Draw one straight line through the center of your data.
Let’s say the footprints at our crime scene are 29cm long, how tall is the person? To figure that out. Start at 29 cm on the x-axis go straight up to the line then straight to the left and read off where you cross the Y-axis. That’s, according to our data, how tall our person in interest is.
How tall is our person of interest? ___________________
So, a few more things
1) Do you think this is a valid technique? Why or why not?
2) Would you be willing to put someone in jail based on what we did here today? What would you want to do better to make sure you were right?
3) Do you think this is a case where fancier equipment would be helpful?
4) Thinking about measuring why wouldn’t you want to measure your height in millimeters and your foot size in miles?
Foot Size Height
32 1.87
30 1.55
31 1.8
30.5 1.83
31 1.85
30 1.71
30 1.83
25 1.5
21 1.23
26 1.66
26 1.63
31 1.81
29 1.82
30 1.8
27 1.67
23 1.53
28.5 1.6
25 1.58
29 1.74