State the relevant situations when primary or secondary data are to be used.
Primary data is used when a researcher has an issue or a study unique to its purpose. In such cases, he/she will have to collect data as per his own requirements.
Ex - if I want to know how many 16 year old are addicted to social media, and the secondary data is available only for the age groups of 20 and above, then I will have to conduct my own research and for that collect primary data
Secondary Data is usually for reference or cross-checking of your own research. Also when the research or study is of small-scale and collection of primary data can be costly in terms of money, energy and time, we can opt for secondary data.