| Date | May 2019 | Marks available | 2 | Reference code | 19M.2.HL:.tz0.1 |
| Level | Higher Level | Paper | Paper 2 | Time zone | time zone 0 |
| Command term | Explain | Question number | 1 | Adapted from | N/A |
Question
A study investigated the effect of plyometric exercise on sprint speed. (Plyometric exercise involves rapid and repeated stretching and contracting of the muscles.) The mean speed of each participant was measured during a 20 m sprint as a baseline and then in a further five 20 m sprints. During the first 75 seconds of the interval between sprints the participants carried out one of the following activities:
- Plyometric: three sets of alternate leg bounds (running-like movement, jumping from one leg to the other consecutively)
- Control: continuous walking.
The graph shows the mean sprint speed and positive standard deviation value for both conditions.
A paired t-test was conducted to compare mean sprint speed at 4 minutes with mean sprint speed at baseline. The results were:
- Plyometric condition: p < 0.05
- Control condition: p > 0.05
Identify the time and condition with the highest mean sprint speed.
Calculate the difference in mean sprint speed, in m s–1, between baseline and at 4 minutes for the plyometric condition.
Using the data, discuss the hypothesis that plyometric exercise can improve sprint performance.
Explain the reason for using a control condition in this study design.
Comment on the meaning of the results from the t-test.
Markscheme
8 minutes
AND
plyometric ✔
[1]
6.75 – 6.55 ✔
= 0.20 «m s–1» ✔
Accept calculations in the reverse.
Consider ECF
[2]
plyometric exercise improved performance / hypothesis is supported ✔
The t-test supports the hypothesis that plyometric exercise improves performance with p<0.05 «at 4 minutes» ✔
plyometric exercise did not improve performance prior to 4 minutes ✔
plyometric exercise was less effective after 8 minutes / plyometric condition speed increased/was better than the control up to the 12-minute test period ✔
For mark point 1, accept the use of the actual data for discussion. Also the reason for the judgement needs to relate to the data.
[2 max]
the control condition allows for a comparison point for the experimenter to compare the subjects’ speed with
OR
control allows one factor to be investigated while all others are kept constant
OR
there are confounding variables in comparing outcomes with baseline data ✔
the control condition allows the researcher to determine warm-up / fatigue effects ✔
control condition increases «internal» validity ✔
[2 max]
the plyometric condition was statistically significantly different (p < 0.05) / null hypothesis should be rejected ✔
the control condition was not statistically significantly different (p > 0.05) / null hypothesis should be accepted ✔
[2]
Examiners report
Overall this question was answered well; however, a few candidates struggled with the fact that two elements were required for this answer.
Overall, the students were able to identify relevant information. The students who were not able to correctly identify the values usually earned 1 mark with a note for an error carried forward (ECF) for the correct result of the calculation but an incorrect choice of values.
This question was answered relatively well; however, too many students made the mistake of perceiving the higher sprint speed as worse performance.
Many students were able to only achieve one mark for stating that the control condition allows for a comparison point.
Too few candidates were able to identify the statistical significance. Many candidates made no reference to data from the t-test.
