MATHEMATICSMethods of Collecting Primary Data

Lesson Objectives

•The aim of this powerpoint is to help you…

• to learn about the different methods of collecting primary data

• to learn how to prepare a data collection table

• to collect some primary data

Methods of Collecting Primary Data

• There are 5 main methods you need to learn about.

• OBSERVATION

• DATA-LOGGING

• CONTROLLED EXPERIMENT

• QUESTIONNAIRE

• SURVEY

Observation

• This is when you collect data by observing and noting down your results.

• BEWARE: To avoid any bias in your results, ensure you think carefully about the location(s) and day(s)/time(s) at which you carry out your observation(s).

• Example: You wish to find out about the types of vehicles driving through the centre of your local town. Pick several main two-way roads passing through the centre. Carry out observations at each point on weekdays and at weekends, at varying times during the day.

Data Logging

• This is where a computer or machine makes observations. If photographs are involved, it may involve undertaking observations at fixed time intervals.

• Example: The town council are considering whether to change a road to a one-way street. They decide to monitor how many vehicles travel in each direction. They do this by using data-logging equipment which is placed at appropriate positions along the road and left there for 2 weeks.

Controlled Experiment• This is when you set up an experiment to collect data. You may

repeat the experiment lots of times or undertake one experiment at the same time on lots of samples.

• BEWARE: To ensure fairness and avoid bias, ensure all control variables are kept constant every time you repeat the experiment or for every sample. To improve the reliability of your results, increase the number of times you repeat the experiment or increase the sample size.

• Example: You wish to analyse pupil reaction times using a computer program. Students must press the space bar when the screen changes colour. You must ensure that all students start sitting in the same position and with the hand they write with already placed on the space bar. The colour the screen changes from and to must also be kept the same.

Questionnaire / Survey

QUESTIONAIRE• This is when you devise a series of questions and their

answer sets, print them out as leaflets and give them out to people you hope will fill them in and return them.

SURVEY• This is when you devise a series of questions and their

answer sets, but you ask people the questions and you note down their answers.

Questionnaire / Survey

• For both questionnaires and surveys, you need to think very carefully about how to word the questions and response sections to avoid bias - more about that later.

• You also need to think carefully about where to hand out the questionnaires or to undertake the survey and who to hand them out to or to question.

• This will very much depend on the reason for the survey and whether it will be comparing different genders, age groups etc.

Data Collection Sheets

• Before drawing up any data collection sheets/tables you need to consider whether the data will be used for comparison purposes, in which case, the table can become more and more complicated and you may need to change your A4 sheet from portrait to landscape!

• Your table will also change depending upon the method you are using to collect your primary data.

• Let’s work backwards through the methods…

Sheets for Surveys

• If you are undertaking a survey, your data collection will be straight forward.

• The first column will contain the questions and the following (up to 6) columns will each contain the possible responses. You would then tick the response you got from each person.

Sheets for Experiment Results

• If you are undertaking a controlled experiment your table will be dictated by the independent and dependent variables.

• The first column will contain the independent variable – the one YOU are setting. All the columns after that will be for the dependent variable, i.e. the values you are collecting or measuring.

Sheets for Observations

• Although you will see examples at the BBC Bitesize website of much larger tables, the number of options you should have (to make analysis much easier to manage later on) is at least 3 but no more than 6.

• The first column will therefore list up to 5 of the most popular expected answers, with the final option being ‘other’ or a value with ‘or more’ at the end. The second (and widest column) should be for the tallies. The third column should be for the frequency (i.e. tallies written as a number).

Sheets for Observations (cont’d)

• Remember to use five bar gates when tallying, i.e. the first four tallies are vertical lines and the fifth tally crosses through these (e.g. |||| ). Totalling them up at the end for the frequency is easier using these gates.

• If you are going to be comparing data across 2 (or more groups), then after the first column you will need a tally and frequency column for EACH group (be it gender, age, ethnic background etc.)

Examples of Observation SheetsExample 1• I wish to find out what the most popular car colour is in my

street. Possible colours are: red, blue, grey, white, black, green, silver, yellow… I need to summarise these in a maximum of 6 options. Here is what I could choose for my table…

Car Colour Tally Frequency

Black    Blue    Red    Silver (inc. Grey)    White    Other    

Examples of Observation SheetsExample 2• I wish to find out what people’s favourite colour of car is,

and whether it is the same for men and women. My original table (for example 1) will need to be adapted as follows…

Car ColourMen Women

Tally Freq. Tally Freq.Black        Blue        Red        Silver (inc. Grey)        White        Other        

Examples of Observation SheetsExample 3• I wish to find out whether different colour cars are driven

by different age groups and whether, within those age groups, there is any difference between men and women. My original table now needs to be adapted as follows:

Car ColourAge 17-32 Age 33-49 Age 50 and over

Men Women Men Women Men WomenTally Freq Tally Freq Tally Freq Tally Freq Tally Freq Tally Freq

Black           

Blue           

Red           

Silver(inc. Grey)

           

White           

Other           

What next?• Print out and read through the notes called Data2a and Data2b.

• To consolidate all the background work you have done so far, and to give you further information on ‘grouping data’ etc., please review the BBC KS3 Bitesize Maths lesson and then the testbite called Collecting and Recording Data found at:

• Lesson: http://www.bbc.co.uk/education/guides/zvybkqt/revision• Testbite: http://www.bbc.co.uk/education/guides/zvybkqt/test

• At the bottom of Data2b notes sheet, you are given some examples of observations or experiments you can carry out yourself and for which you will need to prepare a suitable data collection sheet.

• Now move on to the Data-3 powerpoint