Note 8 : Sampling

1. Note 8: Sampling PPDAC cycle - reminder

2. Sampling involves surveying some of the population. Advantages of sampling include: • Impractical and too time-consuming to survey everyone • Avoids unnecessary expense • Data may be unavailable • Gives a quick ’snapshot’ of the data • Avoids tampering with or destroying all the data

3. A sample must: • be unbiased and representative of the population • be randomly selected • have every member of the population having an equal chance of being chosen

4. Random Sampling • Every member of a population is allocated a number • Use the calculator to generate numbers (Number of items x RAN# + 1 – ignore decimals) • Match the number on the calculator with the relevant data, ignoring repeats • Stop when you have the required number for your sample

5. Example: Select a sample of 4 subjects

6. Note 9: Data Collection Data can be gathered by: • Observation • Interviews • Questionnaires Raw data can be organised into tables when it is collected

7. Example: The 33 students were asked how many times they bought lunch at the canteen. Below is the tally of individual results. 0 4 0 3 5 0 5 5 0 2 1 0 5 2 3 0 0 5 5 1 2 5 5 3 0 0 1 5 0 5 1 3 0 The data can be summarised in a frequency table

8. Page 248 Exercise A and B