S3 June 2017 Q1
1. A company director decides to survey staff about changes to the company calendar. The company has staff in 4 different job roles
72 managers, 108 drivers, 180 administrators and 360 warehouse staff.
The director decides to take a stratified sample.
(a) Write down one advantage of using a stratified sample rather than a simple random sample for this survey. (1)
(b) Find the number of staff in each job role that will be included in a stratified sample of 40 staff. (3)
(c) Describe how to choose managers for the stratified sample. (2)
| Scheme | Marks |
|---|---|
| -(accurate) estimates for each strata / job -more representative of the population -reflects population structure | B1 |
| (1) |
Notes
B1 Any 1 oe
| Scheme | Marks |
|---|---|
| Total staff=720 | B1 |
| Managers \(= \dfrac{72}{720} \times 40 = 4\) | M1 |
| Drivers \(= \dfrac{108}{720} \times 40 = 6\) | |
| Administrators \(= \dfrac{180}{720} \times 40 = 10\) | |
| Warehouse \(= \dfrac{360}{720} \times 40 = 20\) | A1 |
| (3) |
Notes
B1 May be implied by calculations
M1 For one correct calculation, follow through their 720.
A1 4, 6, 10, 20 only. Must identify which job the values relate to.
| Scheme | Marks |
|---|---|
| Label all managers 1 – 72 o.e. | B1 |
| Using random numbers in range 1-72 or 0-71 select 4 (managers). | B1 |
| (2) | |
| (6 marks) |
Notes
1st B1 Idea of sampling frame or list of managers. Need not give the specific term.
2nd B1 Use of random numbers to select required number of managers. Must mention use of random numbers or some random selection process.
If they are describing systematic sampling score B0.