Topic 4 Data Analysis Exam Questions

Q1.
 
Tuberculosis (TB) is an infectious disease caused by mycobacteria.
Individuals infected with M. tuberculosis can be treated with antibiotics.
Four of the antibiotics used to treat TB are shown in the table.

In one clinical trial lasting six months, the effect of treating TB with these antibiotics was investigated.
All patients were treated with all four antibiotics for two months. Then they were treated with different pairs of antibiotics or isoniazid alone for a further four months.
All patients were free of any signs of active TB at the end of the clinical trial.
The design of the trial and the percentage of these patients with TB three years after the trial ended are shown in the diagram.

Analyse the data to comment on the effectiveness of these antibiotics for the treatment of TB.
(6)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 
(Total for question = 6 marks)

Q2.
 
Many plants produce chemicals that have antimicrobial properties.
The suitability of using wood from three types of tree to make kitchen chopping boards was investigated.
In this investigation, 50 cm3 of a bacterial culture was added to 100 g of wood chippings from each of three types of tree.
The growth of bacteria was measured at the start (Day 0), and then after 1, 2, 4 and 8 days.
The results are shown in the graph.

Temperature and the moisture content of wood from pine trees can affect bacterial growth.
Graph 1 shows the effect of temperature on bacterial growth.

Graph 2 shows the effect of temperature on the moisture content of wood.

Analyse the data to deduce the effects of these two factors on bacterial growth on wood from pine trees.
(4)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 
(Total for question = 4 marks)

Q3.
 
Svalbard Global Seed Vault (SGSV) is a seed bank. It keeps seeds from almost 4000 species of plants, focussing on food crops such as wheat, rice and maize.
The purpose of SGSV is to store seeds for use in the future, 50 or more years from now.
Seeds from three varieties of maize were tested to see the effects of long periods of storage. The results of these tests are shown in the graph.

Explain how SGSV could make use of these results.
(3)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 
(Total for question = 3 marks)

Q4.
 
Seed banks store seeds to conserve different varieties of plants.
Seeds are stored for long periods of time in conditions that allow them to be germinated when required.
An investigation was carried out to study the effect of storage time on wheat seeds of two different varieties.
Wheat seeds of one variety, P, were collected and divided into six groups, each with the same number of seeds. Each group of seeds was stored in an atmosphere of 80% humidity at a temperature of 42 °C.
Each group was stored in these conditions for different lengths of time. One group of seeds was germinated immediately after collection. This was the control group.
After storage, the seeds were planted in suitable conditions to allow germination. The number of seeds that germinated was found and the mean percentage germination calculated.
This was repeated using wheat seeds of a different variety, Q.
All other variables were kept constant.
The results are shown in the table.

(i)  Describe the effect of storage time on the germination of seeds for these two varieties of wheat.
(3)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
(ii)  Explain how the results for the control were useful in this investigation.
(2)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 
(Total for question = 5 marks)

Q5.
 
Extracts of the plant St John's wort have also been used to treat depression.
A double blind trial compared the effectiveness of treating depression using a SSRI, an extract of St John's wort, and a placebo.
Depression was measured using the Hamilton Rating Scale for Depression (HRSD). 
The higher the HRSD score the greater the depression.
The table shows the results of this trial.

(i)  State what is meant by the term double blind.
(1)
 ............................................................................................................................................. 
 ............................................................................................................................................. 

(ii)  Analyse the data in the table to compare the effectiveness of these three treatments for depression.
(3)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 

(iii)  Double blind trials give scientists confidence in the results collected.
Explain two ways the design of this trial could be improved in order to increase confidence in the results.
(4)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 

(Total for question = 8 marks)

Examiner's Report

Q1.
 
This was a six-mark levels based question. Examiners read the response and decide on the level of response, they then decide if the response is at the upper mark for that level or the lower mark.
The mark scheme provides guidance on relevant content and on how this might be used to determine a particular level of response.
For this question candidates were provided with information about a clinical trial using different combinations of antibiotics to treat TB patients. They were provided with information on the mode of action of the antibiotics.
Responses that contained only a description of the antibiotic trial results, were considered to be at level 1. Responses that attempted to explain the reasons for differences in the results, were considered to be at level 2, e.g. suggesting that antibiotics with different modes of action or targets work better as combinations. If candidates tried to use information about the mode of antibiotic action with their own understanding e.g. bring in ideas such as dormancy of TB, bacteriostatic and bactericidal antibiotics, if they comment on trial design e.g. missing combinations of antibiotics, then the response is probably at level 3.

Results Plus: Examiner Comments
This response considers in detail all the information provided. The candidate has used information about the results of the trial, about the antibiotics required for a good level 2 response. 
The candidate has also brought in their own biological knowledge and has commented on the design of the trial, extending the quality of response to level 3.

Results Plus: Examiner Tip
Remember to use all the information provided as well as your own biological knowledge and understanding.

 

Q2.
No Examiner's Report available for this question

Q3.
 
Answers generally demonstrated good understanding of the key point, that different types of seed decline in viability at different rates. However, candidates were much less successful in addressing the question of how the seed vault could make use of this information. It was very frequently suggested that varieties A and B were not worth keeping because they would not last long enough, so SGSV should just keep variety C. Clearly this is not how decisions should be made about which seeds should be stored. A reasonable number of candidates made reference to regular germination testing to check for viability, but few explained that as viability begins to drop, the seeds should be grown into plants from which fresh seeds can be collected.

Results Plus: Examiner Comments
This is an example of a good answer that scored 3 marks. The candidate appreciates that the seeds need to be regrown to produce new seeds for storage, in order to maintain viability.

 

Q4.
 
(i)
In this question item, candidates were expected to use the data table to describe the effect of storage time on germination success for wheat varieties P and Q.
A pleasing majority of candidates were able to recognise the reduction in successful germination of both varieties as storage time increased. However, many then simply repeated the data that was presented rather than manipulating it or giving subtrends as described by the third and fourth marking points.
The candidate has given an appropriate overall description of the trend. As the question referred to both varieties of wheat, the trend must apply to both for the award of this mark. However, the candidate does not then either manipulate the data or describe any subtrends.

Results Plus: Examiner Comments
Only the first marking point can be awarded so 1/3.

Results Plus: Examiner Tip
If data is going to be used in an answer, consider whether it should be manipulated in some way. 

In this case, as both varieties are involved, one manipulation per variety was required for the second marking point.

(ii)
In this item, candidates were required to explain how the results of the control were useful in the context of the investigation described in this question.
Whilst all marking points were seen, the first marking point was the most commonly encountered one, with the final marking point being the second most common. It should be noted that many candidates gave generic responses that did not relate to the context provided. This is illustrated in the two examples provided.
In this response, the candidate has only shown that they recognise that the control can be used as a comparison but has not really stated what the comparison is between.

Results Plus: Examiner Comments
No marks were achieved.

This candidate has shown that the control will have a comparison function but has not linked this to both varieties of wheat, nor to being stored.

Results Plus: Examiner Comments
No marks were awarded.

 

Q5.
No Examiner's Report available for this question

Mark Scheme

Q1.

 

Q2.

 

Q3.

 

Q4.

 

Q5.