11.5 Exercises
Selected answers are available in Sect. D.11.
Exercise 11.1 A study of lime trees (Tilia cordata) recorded these variables for 385 lime trees in Russia (Schepaschenko et al. 2017; Dunn and Smyth 2018):
- the foliage biomass, in kg;
- the tree diameter (in cm);
- the age of the tree (in years); and
- the origin of the tree (one of Coppice, Natural, or Planted).
Exercise 11.2 Are these variables quantitative (discrete or continuous, and with what units of measurement?), or qualitative (nominal or ordinal, and with what levels?)?
- Systolic blood pressure.
- Program of enrolment.
- Academic grade (HD; DN; CR; PS; FL).
- Number of times a person visited the doctor last year.
Exercise 11.3 A study of body mass index and its relationship with use of social media (Alley et al. 2017) recorded these variables (among others) from a group of 1140 participants:
- Age (under 45; 45 to 64; 65 or over)
- Gender (male; female)
- Location (urban; rural)
- Social media use (none; low; high)
- BMI (body mass index; the body mass in kg, divided by the square of height in cm)
- Total sitting time, in minutes per day
Gender | Age (years) | Height (cm) | Weight (kg) | GMFCS |
---|---|---|---|---|
M | 9 | 136 | 34.5 | 1 |
M | 7 | 106 | 16.2 | 2 |
M | 7 | 129 | 21.1 | 1 |
M | 12 | 152 | 40.4 | 1 |
M | 11 | 146 | 39.3 | 2 |
M | 5 | 113 | 18.1 | 1 |
M | 6 | 112 | 16.7 | 2 |
M | 8 | 112 | 19.1 | 1 |
M | 8 | 138 | 28.6 | 1 |
M | 6 | 116 | 19.3 | 1 |
F | 7 | 113 | 17.6 | 1 |
M | 11 | 141 | 34.9 | 1 |
M | 7 | 136 | 34.5 | 1 |
F | 9 | 128 | 21.9 | 1 |
F | 8 | 133 | 23.0 | 1 |
Exercise 11.5 A study of fertilizer use (Lane 2002; Dunn and Smyth 2018) recorded the soil nitrogen after applying different fertilizer doses. These variables were recorded:
- the fertilizer dose, in kilograms of nitrogen per hectare;
- the soil nitrogen, in kilograms of nitrogen per hectare; and
- the fertilizer source; one of ‘inorganic’ or ‘organic.’
Exercise 11.7 A study of people who died while taking selfies (Dokur, Petekkaya, and Karadağ 2018) recorded the location (Table 11.3). Which of the following are the variables in the table? For each that is a variable, describe the variable.
- The location.
- The number of people who died at each location.
- The percentage of people who died at each location.
Number | Percentage | |
---|---|---|
Nature, associated environments | 48 | 43.2 |
Train, railway, associated structures | 22 | 19.9 |
Buildings, associated structures | 17 | 15.3 |
Road, bridge, associated structures | 12 | 10.8 |
Dams, associated structures | 7 | 6.3 |
Fields, farms, associated structures | 4 | 3.6 |
Others | 1 | 0.9 |