| Date | May 2015 | Marks available | 2 | Reference code | 15M.3.HL.TZ1.13 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Describe | Question number | 13 | Adapted from | N/A |
Question
For children suffering from persistent asthma, budesonide may be used in inhalers to suppress airway inflammation. This therapy may continue for many years, so its long-term effect on growth was studied. One thousand children were randomly assigned to receive either budesonide or a placebo, a neutral substance used as the control, and were monitored until adulthood. The graph shows the difference in height between the group who received the drug and others who received the placebo (the control group). The same treatment group was measured at the start of the treatment period, four times during the treatment period and then once again about eight years later.
State the mean height difference between the budesonide group and the placebo group at the start of the study.
The mean age for starting the treatment was nine years. Suggest a reason for the choice of this age.
Describe the effect of budesonide on the mean difference in height, during the period of treatment.
Evaluate the long-term after-effect of budesonide treatment on height.
Suggest one significant shortcoming in the data.
Markscheme
a. 0.3 cm (allow 0.2 to 0.4);
b. no difference (because of large error bars);
growing spurt not yet started/prepuberty
a. causes a reduction in height;
b. biggest drop in first year (of treatment);
c. levelling off after two years;
d. no apparent drop after year two because of overlapping error bars;
a. height difference (seen during treatment period) persists into adulthood;
b. budesonide group on average about 1.3 cm/13 mm shorter than placebo group / height difference is (likely) unnoticeable/insignificant compared to placebo group;
c. benefit from budesonide treatment (probably) outweighs (slight) loss of height;
no information on male versus female/diet/ethnic background/health status/medical treatment or history before study/effects on growth at other ages
Examiners report
Almost all were able to use the graph to correctly identify the mean height difference of the two groups.
Most saw that the starting age of participants in the trial was related to puberty as children at 9 years had not yet started their growing spurt.
Candidates struggled to word this answer correctly. Many could get one mark for seeing that it caused a reduction in height but only the better candidates were able to get a second mark. Many seemed to confuse decrease in height with change in height difference between the groups.
Many were able to get one mark for seeing that the height difference persisted into adulthood but few got a second mark.
There were many possible suggestions for shortcomings of the data but there were few good responses.
