A data table associated with The Boat Race is below. It contains the weight in pounds of each team member who participated in The Boat Race, an annual competition between rivals Cambridge University and Oxford University. This data happens to be from the 1992 race.
| Weight (pounds) | School | Position |
|---|---|---|
| 188.5 | Cambridge | Rower |
| 183 | Cambridge | Rower |
| 194.5 | Cambridge | Rower |
| 185 | Cambridge | Rower |
| 214 | Cambridge | Rower |
| 203.5 | Cambridge | Rower |
| 186 | Cambridge | Rower |
| 178.5 | Cambridge | Rower |
| 109 | Cambridge | Coxswain |
| 186 | Oxford | Rower |
| 184.5 | Oxford | Rower |
| 204 | Oxford | Rower |
| 184.5 | Oxford | Rower |
| 195.5 | Oxford | Rower |
| 202.5 | Oxford | Rower |
| 174 | Oxford | Rower |
| 183 | Oxford | Rower |
| 109.5 | Oxford | Coxswain |
As you were researching rowing, you may have noticed the odd needle-like shape of the racing boats. The data above is for a pair of nine-person boats. (Notice that there are 9 people listed under the Cambridge team, and 9 listed under the Oxford team.)
Below is a photo I took of two nine-person boats for your reference.
To get acclimated with this dataset, start by calculating the mean weight of the Cambridge team. Try this now with just a pencil and paper. [1]
Your result should be about 182.44 pounds.
Remember the complex-looking Approach #3 from the Hobbit exercise? It utilized some handy Python tools, including lists, functions, and variables. I am going to use that code as a reference to create something similar for the Cambridge rowing data. Then we'll compare the code output to the answer you calculated by hand.
Type this code and save it as mean-cambridge.py.
After clicking Run, you should get this:
182.444444444 pounds
Line 1:
cambridgeWeights = [188.5, 183, 194.5, 185, 214, 203.5, 186, 178.5, 109]
Lists of data are denoted with a pair of brackets, [ and ]. Each individual data point is separated by a comma, ,. Reading right-to-left, the nine Cambridge teammates' waits are enclosed in a list and then assigned to a new variable called cambridgeWeights. By assigning the list to a variables, you only have to type the data in once. Anytime you want Python to refer to the data, you just mention cambridgeWeights. This saves a lot of typing and makes it easier to read your code.
Line 2:
sumWeights = sum( cambridgeWeights )
Python has a built-in function called sums(), which works with lists. By writing sum(aList) and putting in the name of a specific list, Python will read through the list and add up all the numbers. So you don't have to keep typing sum(cambridgeWeights) every time you need to find the sum of the team, we put the result of sum(cambridgeWeights) into a new variable called sumWeights. Thus, sumWeights has the value 1642.0. Try adding up by hand all the Cambridge weights to confirm that you get the same result.
Line 3:
teamSize = len( cambridgeWeights )
Like sum(), there is also a built-in function that determines the length of a list (i.e. how many pieces of data are in the list). The function is len(). How many individual weights did you add to the list in Line 1? Nine. Thus, the variable teamSize has a value equal to len(cambridgeWeights), which is "9".
Line 4:
mean = sumWeights / teamSize
Using the variables we created earlier, sumWeights and teamSize, divide the former by the latter (i.e. 1642.0 divided by 9) and put the result a variable called mean.
Line 5:
print mean, "pounds"
Display the contents of the mean variable and append the string "pounds" to the end of the line.
| [1] | Recall that the equation for mean is \(\frac{\text{sum of values}}{\text{number of values summed}}\) |
