Basic statistics

Attention
range 3. the width of the class interval = ————————— the number of classes As usual, it is 5, 10, 15 and so on. 组距=全距/组数
4. The frequency distribution must include all the data given. Therefore, the frequency distribution should start: at a value equal to or lower than the lowest number of the ungrouped data end: at a value equal to or higher than the highest number.
3. Determine the width of the class interval
Attention
58, 65, 84, 70, 90, 75, 86, 76, 80, 82, 83, 84, 69, 84, 85, 86, 72, 89, 75, 92
1. The range of the raw data: defined as the difference between the largest and smallest 92-58=34 numbers. too many: cannot achieve generalization 2. The number of classes too few: cannot see the important differences the appropriate number of classes between 5 and 10
Then ,how do we do ? descriptive statistics
inferential statistics
You use descriptive statistics to get to know which strategies are more frequently used by these 400 students .The results you have got are on sample. You may use inferential statistics to examine the relation bewteen the use of strategies and English achievement,or to see whether the male students differ from the female students in their use of stategies based on the notion probability
Class Interval
Frequency
50—under 60 60—under 70 70—under 80 80—under 90 90—under 100 Total
Class Interval 50—under 65 65—under 80 80—under 95
1 2 5 10 2 20
Table 1: Frequency distribution
If the total possible values are various, such as people's age and students' test scores, we need to group the raw data into classes.
Parameter
Parameter is a descriptive measure of the population ,which is denoted by Greek letters such as Page 180.
e.g :
population mean
population variance population standard deviation
Basic statistics
郜战莹 外国语言学及应用语 言学 硕士研究生
Content
A brief description of statistics
Description statistics
Inferential statistics
1.A brief description of statistics
complicated than descriptive,aims at predictions beyond the sample data.
Descriptive Statistics
frequencies
central tendency
variabiபைடு நூலகம்ity
Frequencies
The simplest way to organize the data is to describe their frequency distribution which can reduce and summarize data effectively and efficiently.
Conclusion Descriptive analysis or statistics describes
the general pattern or tendency emerging from the data collected .
Inferential analysis or statistics, more
Generally speaking, we may construct the frequency distribution of these data in three steps:
1. Determine the range of the raw data
2. Determine the number of the classes
In this case, the frequency distribution is concerned with classes rather than with each individual score. How do we describe the frequency distribution in terms of classes? There are no hard-and-fast rules to follow.
Statistic
Statistic is a descriptive measure of a sample , which is denoted by a Roman letter , such as the examples in page 180 e.g. sample mean
sample variance sample standarization deviation
An example:
Suppose you are an English teacher at Nanjing University and you want to know the relationship between the use of strategies and the English proficiency of all the Nanjing University students.There are more than 10,000 students on two campuses.Obviously,you cannnot afford the money and time to take a census. What you may do is to survey 400 students as a sample by a questionnaire.
1.1 Definitions
1.2 Two important terms
1.1
Definitions
descriptive statistics
inferential statistics
1.1.1 Descriptive statistics
If a reseacher is interested only in describing a group from which the data are gathered ,the statistics involved is called descriptive statistics.
c
Note:
In many cases data in the field of applied linguistics are priamrily descriptive in nature.
1.1.2 Inferential statistics
If his or her interest goes beyond describing the group from which the data are collected and s/he tries to draw conclusions about the population from which the group was selected ,the statistics needed in this case in inferential statistics.
Note:
Its advantage is to allow the reseacher to make decisions about the population without studying the entire population.
1.2
Two terms

parameter