1. The World Health Organization wishes to estimate the mean density of people per square kilomete r, they collect data on 56 countries. Justify for full credit. (a) Which of the following is the variable? (i) All countries in the world (ii) Density of people per square kilometer (iii) Set of densities of people per square kilometer of all countries (iv) Set of densities of people per square kilometer of 56 countries (b) Which of the following is the population? (i) All countries in the world (ii) Density of people per square kilometer (iii) Set of densities of people per square kilometer of all countries (iv) Set of densities of people per square kilometer of 56 countries 2. Choose the best answer. Justify for full credit. (a) The hotel ratings are usually on a scale from 0 star to 5 stars. The level of this measurement is (i) interval (ii) nominal (iii) ordinal (iv) ratio (b) In a career readiness research, 100 students were randomly selected from the psychology program, 150 students were randomly selected from the communications program, and 120 students were randomly selected from cyber security program. This type of sampling is called: (i) cluster (ii) convenience (iii) systematic (iv) stratified 3. True or False. Justify for full credit. (a) If the variance from a data set is zero, then all the observations in this data set must be identical. (b) The median of a normal distribution curve is always zero. 4. A school district wanted to assess the effectiveness of a new math readiness program for fifth graders. The school district is divided into the individual fifth grade classrooms and 10 classrooms are randomly selected. All of the children in each of the 10 selected classrooms are assessed. (a) What type of sampling method is being used? (b) Please explain your answer. 5. A study was conducted to determine whether the mean braking distance of four-cylinder cars is greater than the mean braking distance of six-cylinder cars. A random sample of 20 fourcylinder cars and a random sample of 20 six-cylinder cars were obtained, and the braking distances were measured.