1. A market survey was conducted to estimate the proportion of consumers who could recognize the same name of cleanser base on the shape and color of the container. Of the 1,400 consumers, 420 were able to identify the brand name. Using the 99.0 degree of confidence, the population proportion lies within what interval?
2. An experiment involves selecting a random sample of 256 middle managers at random for a study. One item of interest is the mean annual income. The sample mean is computed to be $35,420 and the sample standard deviation is $2,050. What is the point estimate?
3. Manufacturers were subdivided into groups by volume of sales. Those with more than $100 million in sales were classified as Class A Large; those from $50 to $100 million as Class A Medium; and those between $25 and $50 million..., and so on. Sample were then selected from each group. What type of sampling is this called?