简答题 时间序列构成因素有哪些？分解的基本原理和思路是什么？

问答题企业生产一种产品需顺次经过四个车间，这四个车间的废品率分别为1.5%、2.0%、2.0%和1.0%。该企业生产这种产品的平均废品率是多少？

单项选择题The number of phone calls arriving at a switchboard each hour has been recorded and the following frequency distribution has been developed. What is the approximate range of the number of phone calls arriving each hour？（）

A.80
B.200
C.20
D.100

单项选择题The number of phone calls arriving at a switchboard each hour has been recorded and the following frequency distribution has been developed. What is the cumulative frequency of the third class？（）

A.80
B.0.40
C.155
D.75

单项选择题A cumulative frequency distribution would provide（）.

A.a graph of a frequency distribution
B.a running total of the frequencies in the classes
C.the proportion of the total frequencies which fall into each class
D.a very cloudy picture of the frequencies

单项选择题Which of the following is best to show the percentage of a total budget that is spent on each category of items？（）

A.histogram
B.ogive
C.stem and leaf chart
D.pie chart

单项选择题One rule that must always be followed in constructing frequency distributions is that （）.

A.the number of classes must be less than 10
B.each data point can only fall into one class
C.the width of each class is equal to the range
D.the number of intervals must be an odd number

单项选择题One advantage of a stem and leaf plot over a frequency distribution is that （）.

A.it contains more class intervals
B.the values of the original data are retained
C.the class midpoints are used as the stem
D.the class midpoints are used as the leaf

单项选择题The number of class intervals in a frequency distribution is usually between （）.

A.3 and 5
B.7 and 9
C.5 and 15
D.1 and 25

单项选择题A cumulative frequency polygon is also called （）.

A.an ogive
B.a histogram
C.a frequency polygon
D.a stem and leaf plot

单项选择题If the individual class frequency is divided by the total frequency, the result is the （）.

A.midpoint frequency
B.cumulative frequency
C.stem and leaf plot
D.relative frequency

单项选择题If data are grouped into intervals and the number of items in each group is listed, this could be called a （）

A.ogive
B.histogram
C.frequency distribution
D.stem and leaf plot

单项选择题Which of the following is not the goal of descriptive statistics?（）

A.Summarising data
B.Displaying aspects of the collected data
C.Reporting numerical findings
D.Estimating characteristics of the population

单项选择题A student achieves an 82 on the first test in a statistics course. From this, she assumes that her average at the end of the semester (after other tests) will be about 82. This is an example of （）.

A.descriptive statistics
B.inferential statistics
C.nonparametric statistics
D.wishful thinking

单项选择题Which of the following statements is not true？（）

A.One form of descriptive statistics uses graphical techniques
B.One form of descriptive statistics uses numerical techniques
C.In the language of statistics，the term population refers to a group of people
D.Statistical inference is used to draw conclusions or inferences about characteristics of populations based on sample data

单项选择题Descriptive statistics deals with methods of（）

A.organising data.
B.summarising data
C.presenting data in a convenient and informative way
D.doing all of the above