probability and statistic subject

1. Give two reasons why it is sometimes necessary to take a sample from a population. 2. State two ways of obtaining primary data. 3. State two sources of secondary data. 4. State two advantages and two disadvantages of the lottery system for taking a simple random sample from a population. 5. Briefly describe the difference between descriptive statistics and inferential statistics. 6. In your own words, explain and give an example of each of the following statistical terms: (a) population, (b) sample