第二章测试1.A company which makes rechargeable batteries selects some of the batteries for examination. The procedure used chooses two random numbers, say n and m. Starting at the nth battery, every battery at an interval of m is then chosen for examination. This type of sampling is known as: ( )
A:Stratified
B:Multistage
C:Random
D:Systematic
答案:D
2.A company's weekly costs ($C) were plotted against production level (P) for the last 50 weeks and a regression line calculated to be C = 1,000 + 250P. Which statement about the breakdown of weekly costs is true? ( )
A:Fixed costs are $1,000. Variable costs per unit are $250
B:Fixed costs are $250. Variable costs per unit are $4.
C:Fixed costs are $1,000. Variable costs per unit are $5.
D:Fixed costs are $250. Variable costs per unit are $1,000.
3.The value of the correlation coefficient between x and y is 0.9. Which of the following is correct? ( )
A:If the values of x and y were plotted on a graph, the line relating them would have a slope of 0.9.
B:There is a very strong relationship between x and y.
C:There is a weak relationship between x and y.
D:x is 90% of y.
4.The correlation coefficient between A and B is 0.4 and the correlation coefficient between C and D is –0.7. Which of the following statements is correct? ( )
A:There is a stronger relationship between A and B than between C and D.
Which of the following statements about stratification is/are true? ( )
I The sample selected will be representative of the population.
II The structure of the sample will reflect that of the population if the same proportion of individuals is chosen from each stratum.
III It requires prior knowledge of each item in the population.
A:I and III only
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