Statistics
for the
Social
Sciences Handout
Richard
Barton (rick)
richard.barton@dartmouth.edu
Statistical
Consultant 179C
Berry Library
Academic
Computing
http://www.dartmouth.edu/comp/soft-comp/software/statistics/stataintro.html
http://www.dartmouth.edu/comp/soft-comp/software/statistics/statafaq.html
Stata is free software for Dartmouth students; the current version
is 11.
Software that you need can be downloaded from http://www.dartmouth.edu/software Click on the link for Macintosh Software or
Windows Software. Academic Applications
include Stata and KeyAccess. General
Productivity Applications include Stuffit Expander.
Students who bought their computers through Dartmouth should
already have KeyAccess and Stuffit installed.
1) Authenticate to the
download site using your blitzmail name and password.
2) KeyAccess (KSClient)
allows you to run keyserved software.
You must be logged on to keyserver.dartmouth.edu to install and run Stata.
3) Stuffit (Aladdin)
Expander can be used to decompress (unzip) files.
4) Stata (Intercooled).
When you download Stata, you may also receive a file called README
or license.txt that contains information you may need the first time you run
Stata.
You should not register
your copy of Stata or allow automatic updates.
Command Where you issue Stata command
statements.
Results Shows the commands you've entered
and the output of those commands. Upon seeing –more- at the bottom of the
window, enter continues and q quits.
Review Shows the most recent commands
entered. Highlighting a command here enters it in the command window.
Variables Lists the variables in the current
data set. Highlighting a variable here enters it in the command window.
Data editor Opens the current
data set in spreadsheet editor. This window must be closed out to return you to
the command window.
Graph Where graphs are displayed.
A
log file can be opened from the File\Log menu. Open a log file (with a
.log extension) when you start a Stata session to keep a record of what you
type and Stata's output.
Rows
are cases, columns are variables.
.dta indicates a data file
already in Stata format
.txt or .raw indicates data in ASCII (text) formats
.xls indicates data in an
Excel file
Clear Clears data out of memory.
Search If you make a mistake with a Stata command,
it may return an error message along with a return code {for example, r(199)}. The search
command can be used to get a more detailed description of the return code.
Generate Computes a new
variable from an expression.
Most
analysis commands can be followed by a comma and a list of options.
Stata
11 also allows you to do many analyses from the Statistics menu.
Tabulate Gets counts and percents of subgroups for 1
or 2 variables.
Summarize Calculates summary statistics such as means and
sd’s.
Correlate Displays the correlation matrix for a list
of variables.
Regress Fits a linear regression model of a dependent
variable on a single predictor or set of predictors
Stata 11 allows you to build
graphs from the Graphics menu, but it is simpler to build them from the command
window.
Bar
chart |
graph
bar x y z, options |
Histogram |
histogram
x, options |
Scatterplot |
scatter
y x, options |
More on data files
You
may already have a data set that you wish to bring into Stata. The file can be either:
a)
Spreadsheet format (such as Excel);
b)
Tab
(or comma) delimited text format, where variable values always come in the same
order in a line
and separated by the delimiter; or
c)
Fixed
column format, where values for the same variable are always in the same set of
columns for each
case (row).
You
may need a codebook that indicates
the format of the file, what columns hold what variables, how missing values
are defined, what value labels should be applied, etc.
Use Opens a data file that is already in Stata
format. The directory path must be specified and can be obtained
from the
File/Filename menu
Insheet Will read data from a file
that is already in a spreadsheet format
Infile Will read freefield data and tab- or comma-delimited
data from a text file
Infix Will read fixed field data from a text (ASCII) file.
insheet id sex using 'c:\my documents\clients\hsb.raw'
(PC
file path)