AS Science in Society 1.7 Teacher Notes

AS Science In Society 1.7 Teacher notes

How Science Works
Bh, Correlation between a factor and an outcome can be investigated using a case-control study. A sample of cases of the outcome is compared with a matched sample where the outcome is not present
Fc Media reports of scientific developments are always simplified, and sometimes inaccurate. A newspaper report of a new development has not been through the stringent peer review process that articles in scientific journals must undergo (though it may be reporting on work that has).
Gb, Risk is a measure of the probability of harm in a given situation.
Gc We can assess the size of a risk by counting the number of instances of harm in a representative sample of cases. This estimate will be more accurate if the sample size is large, and if instances of harm can be easily and accurately detected. If the probability is very low, it can be very difficult to get an accurate estimate.

Introduction

Media reports of research often use the term ‘risk’ indiscriminately. In this activity students will look at a 2007 newspaper report of research investigating the link between long-term mobile phone use and brain tumours. They will discuss and answer questions on the difference between relative and absolute risk.

The activity

Students should read through the article (clarifying any words they are unsure about) and then answer the questions that follow.

Extension activity

Students could bring in newspaper reports of risk to discuss whether the article is talking about absolute or relative risk.

Suggested answers

1. The authors looked at 11 different studies and compared their results. Suggest why they only considered studies that investigated the effects of long-term mobile phone use.

Many cancers take a long time to develop, so studies which looked at short term use of mobile phone would be unlikely to find any problems.

Need to compare ‘like with like’ studies.

2. Many of the studies used peoples own recollections of how long they used their phone and which ear they held it to. What are some disadvantages of this method of research?

People are very bad at remembering everyday/common things.

Hard to remember how much you used the phone last week, so unlikely to be very accurate about 10 years ago.

People might have given the answers they thought the researchers wanted to hear.

Science Explanations
Bd, Cancers occur when cells divide uncontrollably. Mutations in certain genes damage the normal controls on cell division. The dividing cells form a tumour.

Might have assumed that the cancer was on the side they used the phone, and so say that that was the ear that they used.

Amount they used the phone might have changed over time depending on lifestyle/job etc.

3. The risks in the article are relative risks. What does this mean?

A relative risk compares two different groups of people – in this case phone users with non-phone users.

4. In the UK about 7 per 100,000 people will be diagnosed with brain cancer.

(a) What is the absolute risk for brain cancer in the UK expressed as a percentage?

0.007%

(b) In terms of cases per 100,000 what will be the number of extra cases of glioma (brain cancer) due to long-term mobile phone use?

2.1 (i.e. 30% of 7)

5. What is the absolute risk of brain cancer in long-term mobile phone users?

9.1 per 100 000. (0.009%)

6. Suggest why the newspaper article uses the relative risk rather than the absolute risk in their report.

Appears to show a bigger difference.

Headline grabbing – gets readers attention quickly.

Page 2 ©The Nuffield Foundation, 2008

Copies may be made for UK in schools and colleges

AS Science In Society 1.7 Student sheets

Talking risk

When newspapers, and other media, report risk they use different ways to discuss the risks. How the numbers are reported can change the way we think about the risks.

Read the extract from a newspaper, and then answer the questions that follow.