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Connections - Introduction

A worked example

You can use a computer to help you test out hypotheses.

This activity is an example of how you would do it. Follow the activity through, step by step, and it will help you later when you have to design one of your own.

The activity is called "Making links – age and identifying marks"

Think about the distinguishing marks that people have - scars, birthmarks, moles, burns etc. Some people are born with marks and pick up others as they get older. Perhaps they tip boiling water onto their leg or hit their thumb with a hammer. Some people start off with no marks and collect some later.

So you might well think that the longer people live the more chance they have of picking up identifying marks.

This is a hypothesis

At the moment, though, we don't know for certain whether or not our idea is true. We must try and prove or disprove our hypothesis. This is one of the things that databases are useful for doing.

To test our prediction we will use the datafile to find the average age of prisoners with identifying marks and the average age of those without.

If our hypothesis is correct we can predict that prisoners with identifying marks will be older than prisoners without identifying marks.

Step 1
The first step is to pick out the people who have no distinguishing marks.

To do this carry out a search.

Check that the people now shown in the list do not have any distinguishing marks.

Step 2
The second step is to find the average age of the people with no distinguishing marks.

When you have done this you should find that the average age of people without distinguishing marks is 30. If our prediction is correct then the average age of people with marks should be more than this.

Step 3
The third step is to carry out the same procedures to discover the average age of people with distinguishing marks.

You'll probably need to carry out the search exactly as before except that this time you must 'exclude' the people with no distinguishing marks.

This search finds all the people with no distinguishing marks and then rejects them so only the people who do have marks are left for you to see

Step 4
Now comes the big moment – to see if our hypothesis is correct.

Find the average age of people with distinguishing marks.

You should find that the average is 28.7 years.

This is actually less than the average for people with no marks. So our prediction was not correct.

This may seem like a bad answer but it is not. A hypothesis is a theory. The computer datafile will let us test the hypothesis to see if it is correct. Whether the hypothesis is right or wrong, we have learned something valuable and can move on to the next hypothesis.

The next activities will help you form and test your own hypotheses.