1. Hsien-Ming Lien Dept of Public Finance, NCCU
Examine the data
Hsien-Ming Lien
Dept of Public Finance, NCCU

2. 1.1 Read the data Read the ASCII file Read the excel 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

3. cd
dir
use
save

4. use http://www.ats.ucla.edu/stat/stata/webbooks/reg/elemapi

8. 1.2 Describe the data Describe the data Data size Observations
Variable name
Variable type (string, byte, float, etc)

10. 直接按ok

12. 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

13. List
All observations
Some observations
Some variables

18. 選取變數

21. Notice the missing values of meals. 

22. Codebook
Number of values
Missing values
Distribution of values

24. 選取變數後按ok

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

28. 選取變數後按ok

33. 1.3 Tab the data
Tabulate
Tabulate the size of class size

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

46. 1.4 Graph the data Use graphs to examine the data Histogram
Stem and leaf plot

54. 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.

55. Quiz 1: do a histogram on full
Quiz 2: do a stem-and-leaf plot on full

58. 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.

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

66. 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.

70. Two ways graphs
Scatterplot: show the joint distribution of two variables
Let's look at the scatterplot matrix for the variables:

75. 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

82. save elemapi, replace