3. In the context of sampling, explain the difference between item non-response and unit non-response. 4. You work for a market research company and your boss has asked you to carry out a random sample survey for a car company to identify whether a new car model is attractive to females. The main concern is to produce results of high accuracy. You are being asked to prepare a brief summary containing the items below. (a) Choose an appropriate probability sampling scheme to use. Provide a brief justication for your answer. (b) Describe the sampling frame and the method of contact you propose to use. Briey explain the reasons for your choices. (0) Provide an example in which selection bias may occur. State an action which you would take to address this issue. ((1) State the main research question of the survey. Identify the variables associated with this question. 5. (a) Dene each of the following terms. 1. Simple random sampling. ii. Stratified random sampling. (b) Why might a researcher prefer to take a stratied random sample rather than a simple random sample? Give two reasons. (c) You have been asked to design a nationwide survey in your country to find out about the smoking habits of adults. Give two stratication factors you might use, and explain why you have chosen them