- A In A Certain County There Are Three Towns A B And C The Household Population Sizes In These Towns Are 1000 1500 1 (80.75 KiB) Viewed 37 times
- A In A Certain County There Are Three Towns A B And C The Household Population Sizes In These Towns Are 1000 1500 2 (93.4 KiB) Viewed 37 times
a. In a certain county, there are three towns: A, B, and C. The household population sizes in these towns are 1000, 1500, and 2000, respectively. Assume that a random sample of 50 households is selected by simple random sampling respectively from each of the three towns so that the total sample size is 150 households. Which of the following sampling methods is used in the described example? (1) systematic sampling (2) cluster sampling (3) stratified sampling (4) convenience sampling b. Which of the following statements is TRUE? (1) A parameter is a fixed number that described the characteristic of the random sample. (2) A sample mean X denotes a biased point estimator of the population mean . (3) A sample mean ő is called a point estimate. (4) All of the above (5) None of the above c. Let Xi and X, denote two discrete random variables. Which of the following is always TRUE? (1) E(X1 + X2) = E(X1) + E(X2) (2) Var(X1 + X2) = Var(X1) + Var(X2) (3) SD(X1 + X2) = SD(X1) + SD(X2) (4) All of the above (5) Both (1) and (2) 2
d. After taking a college Spanish course, two groups of students were given a Spanish compre- hension test. Group 1 had never learned Spanish before while group 2 had previously taken a Spanish course in high school. The following graph shows a boxplot of the test scores for the two groups 100 08 09 Test Score 40 20 0 group 1 group2 Based on the boxplot, which of the following statements is TRUE? (1) The median of test scores for group 1 was higher than for group 2. (2) The interquartile range of test scores for group 1 was higher than for group 2. (3) The distribution of test scores for group 1 is left-skewed. (4) About 75% of test scores for group 1 is below 40. (5) About 25% of test scores for group 2 is below 70. e. Suppose that two events A and B are disjoint with P(A) = 0.4 and P(B) = 0.3. Which of the following is TRUE? (1) P(ANB) = 0.12 (2) P(AUB) = 0.58 (3) P(An BC) = 0.4 (4) Both (1) and (2) (5) All of the above