Exercise tests

Question 1

It is possible to test for signs of heart disease using an exercise test. This involves the patient doing a controlled period of exercise whilst their heart rate is monitored.

Scientists measured the heart rates of 700 healthy adult males aged between 25 and 54 before, during and after an exercise test. The test involved running on a treadmill at different speeds. Their results are shown in the graph below in the form in which they were presented.

(a) Suggest two variables the scientists would have controlled during the exercise test.

Answer 1

. Length of time of exercise;

2. Difficulty of exercise;
3. An environmental factor;

Answers about variables relating to the subjects themselves are not valid.

2. E.g. speed of treadmill / running, incline on treadmill.
3. E.g. temperature / humidity / clothing worn.

Question 2

A student determined their pulse rate when sitting down. Describe how they could have investigated whether their results were typical of all students of their age.

Answer 2

1. Obtain pulse rates for a large number of students;

Accept this idea for carrying out the investigation or for collecting data from other scientists work / published data

2. (belonging to) a range of different sexes / ethnic groups/from different parts of the country / employment groups;

Accept suitable alternative variables but the idea of a range must be included

Reject generic references to controlling these variables

3. Calculate mean and standard deviation (of students their age);

Allow ‘calculate standard error / 95% confidence limits / t test / statistical test’

4. See if their mean lies within the standard deviation;

Accept ‘see if my mean lies within the 95% confidence limits’

If statistical test used, accept ‘see if there is a significant difference between means’

Question 3

On each occasion that a patient’s FEV1 was measured, a doctor repeated the measurement several times. Explain why.

Answer 3

(Allows) anomalies to be identified / ignored / effect of anomalies to be reduced / effect of variation in data to be minimised / concordant results;

Accept: ‘outliers’ instead of anomalies

1. Reject: idea of not recording anomalies / preventing anomalies from occurring
2. Accept: ‘cancels out anomalies’ as bottom line response
3. (Makes) average / mean (more) reliable;

Question 4

All the patients continued with their normal treatment for asthma. The normal treatment was the same for all patients and its effects were short-lived. The patients were told to stop this treatment 24 hours before FEV1 measurements were taken.

(i) Suggest why all the patients were allowed to continue with their normal asthma treatment in this investigation.

Answer 4

Unethical / unfair not to treat patients;

2. Dangerous / could cause an asthma attack;

Question 5

After 60 days, the patients in each group were asked to give themselves an Improvement Score from 0-10 to show how much they felt their symptoms had improved. This was done before their FEV1 was measured. The scientists calculated the mean Improvement Score for each group.

(i) The scientists concluded that the data obtained for the Improvement Scores were less reliable than the data obtained measuring FEV1 . Suggest why they concluded this.

Answer 5

Improvement scores) are qualitative / subjective / rely on own judgement / different patients may assess symptoms differently;

Accept: converse arguments for measuring FEV1 e.g. quantitative / objective patients cannot lie

2. Some patients may lie / exaggerate / want to please doctors;
3. Neutral: empirical evidence