Data Management

連賢明政大財政

2

統計軟體

一般通用 STATA SAS

個體計量 LIMDEP

高階軟體 MATLAB GAUSS

3

STATA 優點

容易上手執行速度快軟體可永久性使用網站建構相當完整

http://www.stata.com/ http://www.ats.ucla.edu/stat/stata/

電腦記憶體要多

Stat/Transfer

將其他檔案格式轉為 STATA 資料檔 Stat/Transfer 可支援的檔案類型

Excel Limdep SAS SPSS Many others

Stat/Transfer

Input File Type : 選取原始資料的檔案類型 File Specification ：輸入原始資料檔的路徑 Output File Type ：選取欲轉換之檔案類型 File Specification ：輸入轉換後資料檔欲儲存

之路徑

Stat/Transfer

Variables 標籤下勾選需要的變數

STATA 介面

The command window ：撰寫程式 The result window ：執行程式後之結果 The review window ：顯示執行過的程式 The variable window ：列出所有變數

1.1 Read the data

Read the ASCII file infile must provide the variable name, width, and

format Read the excel file

insheet variable names need to be specified

Read the Stata file use c:\regstata\elemapi from the internet

cd dir use save

1.2 Describe the data

Describe the data Data size Observations Variable name Variable type (string, byte, float, etc)

直接按 ok

Variables api00/academic performance of the school acs_k3/the average class size in kindergarten

through 3rd grade meals/the percentage of students receiving

free meals full/the percentage of teachers who have full

teaching credentials

List All observations Some observations Some variables

選取變數

Notice the missing values of meals. 

Codebook Number of values Missing values Distribution of values

選取變數後按 ok

summarize Provide concise information about variables Observations Basic statistics (mean, s.d., min, max) Option: details

選取變數後按 ok

1.3 Tab the data

Tabulate Tabulate the size of class size

Look at the school and district number to check if they are from the same district

1.4 Graph the data

Use graphs to examine the data Histogram Stem and leaf plot

A stem-and-leaf plot would also have helped to identify these observations.  

This plot shows the exact values of the observations, indicating that there were three -21s, two -20s, and one -19.

Quiz 1: do a histogram on full

Let's look at the frequency distribution of full to see if we can understand this better. 

The values go from 0.42 to 1.0, then jump to 37 and go up from there. It appears as though some of the percentages are actually entered as proportions, e.g., 0.42 was entered instead of 42 or 0.96 which really should have been 96.

Again, let's see which districts these data came from.

We note that all 104 observations in which full was less than or equal to one came from district 401. 

Let's count how many observations there are in district 104 using the count command.

Two ways graphs Scatterplot: show the joint distribution of

two variables Let's look at the scatterplot matrix for the

variables:

api2000

avgclasssizek-3

pctfree

meals

pct fullcredential

400 600 800 1000

-20

0

20

-20 0 20

0

50

100

0 50 100

0.00

50.00

100.00

Correct the variable mistakes

acs_k3 Replace the negative values into the positive

ones replace acs_k3=-acs_k3 if acs_k3<0

Full Change from the percentage to the proportion replace full=full*100 if full<=1

save elemapi2, replace