Fridge Pickers

Purpose

In this unit, using our fridge as the context, we collect data and present these as dot plots and bar graphs. We start to learn about using the computer to display our data.

Achievement Objectives
S3-1: Conduct investigations using the statistical enquiry cycle: gathering, sorting, and displaying multivariate category and whole-number data and simple time-series data to answer questions; identifying patterns and trends in context, within and
Specific Learning Outcomes
• Plan a statistical investigation.
• Display data in dot plots, strip graphs and bar charts.
• Discuss features of data display using middle, spread, and outliers.
Description of Mathematics

Planning an investigation at this level is more complex than at Level 2. Students can conduct investigations using the statistical enquiry (PPDAC) cycle.  The PPDAC cycle stands for problem, plan, data, analysis, and conclusion. Here the students can begin to talk about situations they have experienced, pose investigative questions, and produce a plan for a statistical investigation. Students may be capable now of incorporating a computer into their work. In this unit the students are introduced to dot plots and bar graphs. Depending on the nature of the investigative questions they are posing they will find out that they need to collect and organise the data in different ways. When considering the data, they now start to see and talk about distinctive features of their displays such as the groupings and modes.  Planning a statistical investigation – level 3 provides a full description of all the phases of the statistical enquiry cycle.

Dot plots

Dot plots are used to display the distribution of a numerical variable in which each dot represents a value of the variable.  If a value occurs more than once, the dots are placed one above the other so that the height of the column of dots represents the frequency for that value. Sometimes the dot plot is drawn using crosses instead of dots. Dot plots can be used for categorical data as well.

Bar graphs

In a bar graph equal-width rectangles (bars) represent each category or value for the variable. The height of these bars tells how many of that object there are.  The bars can be vertical, as shown in the example, or horizontal.

The example above shows the types of shoes worn in the class on a particular day. There are three types of shoes: jandals, sneakers, and boots. The height of the corresponding bars shows that there are six lots of jandals, 15 lots of sneakers and three lots of boots. It should be noted that the numbers label the points on the vertical axis, not the spaces between them. Notice too, in a convention used for discrete data (category and whole number data), there are gaps between the bars.

The learning opportunities in this unit can be differentiated by providing or removing support to students and by varying the task requirements. Ways to support students include:

• setting up the plan for data collection for students to follow
• the type of data collected; categorical data can be easier to manage than numerical data
• the type of analysis – and the support given to do the analysis
• providing pre-prepared graph templates to support developing scales for axes
• providing prompts for writing descriptive statements
• teacher support at all stages of the investigation.

The context for this unit can be adapted to suit the interests and experiences of your students. The statistical enquiry process can be applied to many topics and selecting ones that are of interest to your students should always be a priority.

Required Resource Materials
• Memo cube paper or sticky notes – three different colours
• Copymasters One, Two and Three
Activity

Session 1

We begin the week collecting fridge data about our class. We use this information to start to explore new types of data displays.

1. Tell the class that this week they will be investigating Fridge Pickers.
What do you think a fridge picker is?
Collect ideas from the class and put on the board or a chart.
2. Tell the class that the first thing we will investigate is What types of foods do the students in our class like to pick from the fridge? This is the investigative question (our problem).
3. As part of the planning for the investigation we need to establish how we will collect the data that we need to answer the investigation question.  We will use the following survey question – but we need to do some work with it so that we have only a few categories, it is possible that every student in the class might have a different choice ­– What type of food do you like picking from your fridge?  Start by getting the students to give responses to the question: What food do you like picking from your fridge?
4. List the ideas on the board and then group into 5-6 categories with one of these categories being an “other” category. From here develop the final survey question: What type of food do you like picking from your fridge – choose from: OPTION 1, OPTION 2, OPTION 3, OPTION 4, OPTION 5, OTHER please specify _________
5. As well in this introductory activity we are going to add an additional variable to the data set, starting to introduce the idea of having more than one variable to work with.  For example: It might be interesting to see if the place in the family has any effect on the type of food they pick from the fridge. To explore this further idea, we will collect data on the position they are in the family - are they the oldest, middle, youngest child – as well as their favourite type of food to pick from the fridge. How do we define position? Oldest – no siblings older than you; Middle – have older and younger siblings; Youngest – you have older sibling(s), but no siblings younger than you. An only child would be the oldest; if there are two children then there is an oldest and a youngest, from three children onwards a middle child (or children) become possible.
6. Give students a small, coloured square of paper (or a sticky note) based on their position in the family.  For example: Oldest child – yellow; middle child – green; youngest child – blue.   Then ask them to give the answer to the survey question from #3. They select one of the categories to either write or draw on the paper. Collect the data.
7. Collect in the paper (sticky notes) and ask the students to sort the squares to make a bar graph (analysis).  If possible, take a photo of the display, upload into a google doc or similar and capture student statements about the display.
What statements can you make about us as fridge pickers? (analysis)
8. If it has not come up, ask the students what they notice, if anything, about the colours in the graph. Maybe rearrange the squares so that the same colours are together in each of the stacks. Take a picture of the new display and add to the document.
Does the display show us anything different?
9. Rearrange the squares so that the same colours are together in a bar graph.  What does this now show us? The distribution of position in the family. What do you notice about this graph? (Take a picture of the new display and add to the document). E.g. More people are the youngest in their family in our class than are the oldest in our class.
10. Sort the squares in the family position stack into groups by the type of food they like to pick. (Take a picture of the new display and add to the document). How is this display different to the one we had when we had sorted by type of food?  Does if give us any different information?
11. Communicate findings (conclusion). Refer to the investigative question at the start: What types of foods do the students in our class like to pick from the fridge?  and write and answer based on the findings from the explorations above.

Preparation for data collection for a home-based activity

How many people in your family do you think are fridge pickers?
What time of the day do you think people fridge pick?
How could we find out?
2. Show the students the Fridge Pickers (Copymaster 1dot plot and highlight its features. Explain that they are to use it at home one day this week to investigate fridge pickers. Each time a person opens the fridge to pick they are to put a X beside the time. If you want to add individual detail, ask each member of the family to use a different coloured pen or to write their Initial instead of a X. The dot plots are to be brought to school for the activity in session 5.

3. As a class make predictions about the information they will gather.
We think that:
Our fridges will be opened the most before teatime.
That no one will open the fridge between midnight and 6 am.
4. Ask each child to write an additional 1-2 statements about who they think will open the fridge the most in their home and when the most popular times will be.

Sessions 2-4

Over the next three days the students gather information around the theme of fridges or food. They will collect and record the data in a spreadsheet or data table in a software package that allows them to draw statistical displays.  In this unit we use CODAP, but other packages can do similar things.  Look for software tools that allow them to have the raw data (i.e. one row containing the responses for each person or object they collect data on) rather than needing summarised data.  Using the statistical graphing tool students will display the information using dot plots and bar graphs, and make statements about what the data shows. If you do not have access to computers then provide students with blank templates to make their dot plots or bar graphs (Copymaster 3).

PROBLEM: Generating ideas for statistical investigation and developing investigative questions

1. Brainstorm ideas for other fridge or food investigations. List these on the board. Some ideas could include:
• What drinks do we keep in our fridges?
• What type of fridges do we have?
• What are our favourite frozen vegetables?
• What types of yoghurt do we like?
• What brands of margarine do we prefer?
2. Let the students work in pairs to investigate using the PPDAC cycle. First ask the students to select a topic. If two or more pairs want to do the same investigation, let them do so. When it comes to sharing findings remember to compare results.
3. Students develop an investigative question(s) based on their topic. These are the questions they ask of the data; it will be the question(s) we explore using the PPDAC cycle.
Prompts to help with posing investigative questions include:
• Do you want to describe something (summary) or compare something (comparison)?
• Summary questions have one variable and one group e.g. What types of fridges do we have? [type of fridge, we (our class)]; What brands of margarine do the students in Room 23 prefer [preference of margarine brand, students in Room 23]?
• Comparison questions have one variable and two or more groups e.g. How do the types of yoghurt our class like compare with the types of yoghurt Room 21 like?
4. Check the investigative questions that students have posed.  Gather them in e.g. write on the board, type into a google doc or write on paper to be pinned up.  As a class check each investigative question for the variable and the group and the remaining criteria:
• Is the question purposeful?
• Is the question about the whole group? Check that it is not just finding an individual or smaller group of the whole group.
• Is the question one that we can collect data for?
• Is it clear that the question is a summary investigative question or a comparison investigative question?
5. Get students to make a prediction about what they will find as a result of their investigation.

PLAN: Planning to collect data to answer our investigative questions

1. Students need to develop survey questions to answer their investigative question. For example, if they are exploring the investigative question What are the types of fridges we have? they will need to get information to answer this question.  Survey questions are how they get the information. In thinking about their investigative question, the students decide they want to find out about the make and the style of the fridge. They pose two survey questions: (1) What is the make of your fridge? and (2) What type of fridge do you have? In discussing with another pair at their table they wondered about what would happen if people had two fridges because one of the students at the table said they had a fridge in the kitchen and one in the garage that was used for drinks and extra food.  They decided to add to their survey questions – if you have more than one, pick the one that is your main fridge.
2. Once the students have developed their survey questions they should list some options for people to choose from:
For example: Make of fridge question – using the internet they found 15 different makes of fridges so they picked six that they knew and added an “other” category.
Categories: Fisher and Paykel, Haier, LG, Samsung, Simpson, Westinghouse, Other
Type of fridge question – using the internet they found the following categories for refrigerators: All refrigerator, Top (freezer) mount refrigerator, Bottom (freezer) mount refrigerator, single-door refrigerator with freezer capacity, Side by side refrigerator, French door model refrigerator, other.
3. Finally, the students need to prepare instructions for their survey, i.e., they need to prepare instructions to indicate how others are to respond to their survey questions. At this stage they should also think about how to collect the data, for example using a table to record responses.
 Your name Q1. What is the make of your fridge? If you have more than one, pick the one that is your main fridge. Choose from: Fisher and Paykel Haier LG Samsung Simpson Westinghouse Other – please specify Q2. What type of fridge do you have? If you have more than one, pick the one that is your main fridge. Choose from: All refrigerator Top (freezer) mount refrigerator Bottom (freezer) mount refrigerator Single-door refrigerator with freezer capacity Side by side refrigerator French door model refrigerator Other – please specify
4. To check the clarity of the survey questions and instructions have pairs exchange and check one another’s.
Are they clear to you?
Can you tell what you are supposed to do?
What do you think they need to change to make the directions clearer?
5. Allow time for the survey questions and instructions to be modified.

DATA: Collecting and organising data

1. Tell the pairs to leave their instructions and tables to record the responses at their desks. This could be in paper format or electronic.  Electronic versions could be set up directly in a spreadsheet e.g. google sheets or excel or use a word document, e.g. word, google docs, with a table set up. Have the students rotate around the room completing the other students' surveys.
 Your name Q1. What is the make of your fridge? If you have more than one, pick the one that is your main fridge. Choose from: Fisher and Paykel Haier LG Samsung Simpson Westinghouse Other – please specify Q2. What type of fridge do you have? If you have more than one, pick the one that is your main fridge. Choose from: All refrigerator Top (freezer) mount refrigerator Bottom (freezer) mount refrigerator Single-door refrigerator with freezer capacity Side by side refrigerator French door model refrigerator Other – please specify Melino Simpson Bottom mount Ngaire Fisher and Paykel Bottom mount Wiremu Fisher and Paykel Bottom mount Tui LG French door model Anna Haier Side by side Jimmy Other – Daewoo Top mount Jackson Fisher and Paykel Side by side
2. After the surveys have been completed the pairs return to work with the data collected.
3. If an electronic means of collecting the data was not used get students to enter the data collected into a spreadsheet or a data table in CODAP.  A simple way to do this is using the table tool in CODAP.  See this video on how to do this. If students already have the data in a spreadsheet see this video on how to import data from a spreadsheet into CODAP.

ANALYSIS: Making and describing displays

An introduction to using CODAP as a tool for statistical investigations is explained in full in Planning a statistical investigation – level 3 (session 5).

As mentioned earlier if you do not have access to computers then provide students with blank templates to make their dot plots or bar graphs (Copymaster 3).

Possible examples of the types of information students can get on CODAP is below.  In these examples the investigative question What are the types of fridges we have? is explored by graphing the two variables separately and then combined.

These first two graphs show the make and then the type of fridge.  Because we are using technology, we can also quickly explore the combination of the two variables.

Once students have generated their graphs, they can start to describe the displays.

To describe the display, encourage students to write “I notice…” statements about their displays.  If students are not sure what to notice the teacher can prompt further statements by asking questions such as:

• What do you notice about the most common …?
• What do you notice about the largest number… the smallest number…?
• What do you notice about where most of the data lies…?
• What do you notice about the most popular… least popular…?
• What do you notice about the type of fridge for Fisher and Paykel compared with the type of fridge for Mitsubishi (more specific example for a comparison) …?

Check the “I notice…” statements for the variable and reference to the group.  For example: “I notice that the most common make of fridge for our class in Fisher and Paykel.” This statement includes the variable (make of fridge) and the group (our class). Support students to write statements that include the variable and the group.

1. Discuss with students the features that you want them to include in their report (or poster) of the statistical investigation. The reports could include:
• Their investigative question .
• What they predicted they would find as a result of their investigation.
• A description of how the data was collected, including their survey questions and any decisions they made and why.
• The data displayed using bar graphs and/or dot plots.
• A written description of the data and an answer to their investigative question.
2. Display the completed investigations. Give the students time to look at the other investigations before discussing.
Tell some of the things you learned from the investigations. What are the preferences of students in our class?
What was the most popular choice in your survey?
How can you tell?
How many students made that choice?
Which display is most effective?
Did you have any unexpected results?
3. Compare investigations completed by more than one pair.
Do these displays look alike?
Did the two surveys have the same choices for you to make?
What differences are there between the investigations?

Session 5

In today’s session we use the data we have gathered at home to examine our initial predictions about fridge pickers.

1. We begin this session by looking at the dot plots that the students have created at home.
Which times of the day are the busiest for fridge pickers? Why?
Which times of the day are the quietest? Why?
Who opens the fridge the most often in your home?
2. Ask the students to make a poster displaying the results of their fridge picker investigation. List the requirements for the poster for the students to complete, for example:
• Display your data using a dot plot