Student worksheet

Thought starters: when you think about a contaminated drink, what comes to mind?

Step 1

What happens to our recycling?

Brainstorm the types of materials that can be recycled and the types of materials that cause contamination.

Step 2

EU Recycling

Mathematics Terms

Mean: is the sum of all the values divided by number of items for which there are values.

Median: is the middle value out of a series of values. All the values are lined up from smallest to largest and the middle value is lined up. When there is an even number of values, then there will be two values that are in the middle. In this case, the average of the two values is the median. This can be a valuable way to analyse data when some of the data distorts the mean. An example is the average wage and the mean wage can be different because a few high wage earners can have a large effect on the mean. It is useful to compare the mean and medium.

Mode: is the most common value. When there are two common values which are the same, it is called bimodal.

This graph displays data for the recycling rates of packaging waste materials for the EU countries. The recycling rate is measured as a percentage of material recycled:

Source of this graph

1. How many countries are on the graph?

2. Calculate the mean. Divide the addition of all the percentages by the total number of countries.

Mean =

3. Order the countries from highest to lowest.
a) Which country is the median?

b) What is the percentage value for this country?

4. Which countries make up the mode and what is their percentage value?

5. Outliers are values that are very different to the rest of the data. Are the percentage rates for some countries very different?

6. Which countries are outliers?

7. Attempt to explain what might be different to these countries compared to the other EU countries that would make their percentage so different.

8. Write your mean, medium and mode into the table below.

Compare the mean, medium and mode.

9. Do the outliers distort the mean? How can you tell?

10. When analysing data why is it useful to compare the mean, medium and mode?

Step 3

Analysing School Waste Survey

122 students answered questions about their waste that was related to food and drink:

They provided information about their waste for a day from the time they left home to go to school to when they arrived back home.
They provided information about the type of waste and the number of each type.
They provided information about what they did with each type of waste. They were given the option of rubbish bin, recycling bin, compost bucket or litter. Anything that went back home was not considered waste.
In the first table of data, any waste not properly disposed of such as contamination and litter were highlighted in grey. Some paper products could have been rubbish, recycled or composted depending on the condition of the paper.

Get a copy of the excel sheet - download here: Student Survey Data Sheet

Examining the waste items per person

1. What is the mean for the student waste?

2. What is the median for the data?

3. What is the mode?

For each type of waste, convert to a percentage that which was not properly disposed of.

4. What is the mean for the student waste that was not properly disposed?

5. What is the median for the data not properly disposed?

6. What is the mode for the data not properly disposed?

7. Are there any outliers?

If you had to fix this school’s waste system

What would an outlier with a small percentage mean about the disposal of the waste?

What would an outlier with a high percentage mean about the disposal of the waste?

The contamination rate of recycling materials is often around 5%. Is the contamination rate that goes into the recycling bin and compost bucket higher or lower than 5%.

Part 4

Recycling contamination sticker

You are now an expert on recycling bin contamination. Design a simple sticker that could go onto a recycle bin that simply explains to the household what not to put into the bin.

These Planet Ark resources were developed by Cool.org with funding from the Alcoa Foundation.

National Recycling Week - Using Maths to Reduce Contamination

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