Data Modelling (ITECH2004)

Each of 16 students measured the circumference of a tennis ball by four different methods,
which were:
Method A: Estimate the circumference by eye.
Method B: Measure the diameter with a ruler, and then compute the circumference.
Method C: Measure the circumference with a ruler and string.
Method D: Measure the circumference by rolling the ball along a ruler.
The results (in cm) are as follows, in increasing order for each method:
Method A: 18.0, 18.0, 18.0, 20.0, 22.0, 22.0, 22.5, 23.0, 24.0, 24.0, 25.0, 25.0, 25.0, 25.0,
26.0, 26.4.
Method B: 18.8, 18.9, 18.9, 19.6, 20.1, 20.4, 20.4, 20.4, 20.4, 20.5, 21.2, 22.0, 22.0, 22.0,
22.0, 23.6.
Method C: 20.2, 20.5, 20.5, 20.7, 20.8, 20.9, 21.0, 21.0, 21.0, 21.0, 21.0, 21.5, 21.5, 21.5,
21.5, 21.6.
Method D: 20.0, 20.0, 20.0, 20.0, 20.2, 20.5, 20.5, 20.7, 20.7, 20.7, 21.0, 21.1, 21.5, 21.6,
22.1, 22.3.

b. Compute the median measurement for each method.

Each of 16 students measured the circumference of a tennis ball by four different methods,
which were:
Method A: Estimate the circumference by eye.
Method B: Measure the diameter with a ruler, and then compute the circumference.
Method C: Measure the circumference with a ruler and string.
Method D: Measure the circumference by rolling the ball along a ruler.
The results (in cm) are as follows, in increasing order for each method:
Method A: 18.0, 18.0, 18.0, 20.0, 22.0, 22.0, 22.5, 23.0, 24.0, 24.0, 25.0, 25.0, 25.0, 25.0,
26.0, 26.4.
Method B: 18.8, 18.9, 18.9, 19.6, 20.1, 20.4, 20.4, 20.4, 20.4, 20.5, 21.2, 22.0, 22.0, 22.0,
22.0, 23.6.
Method C: 20.2, 20.5, 20.5, 20.7, 20.8, 20.9, 21.0, 21.0, 21.0, 21.0, 21.0, 21.5, 21.5, 21.5,
21.5, 21.6.
Method D: 20.0, 20.0, 20.0, 20.0, 20.2, 20.5, 20.5, 20.7, 20.7, 20.7, 21.0, 21.1, 21.5, 21.6,
22.1, 22.3.
a. Compute the mean measurement for each method.