alpha.hlp

是一个经济学管理应用软件 很难找的 但是经济学学生又必须用到

{smcl}
{* 20jan2005}{...}
{cmd:help alpha}{right:dialog:  {bf:{dialog alpha}}}
{hline}

{title:Title}

{p2colset 5 18 20 2}{...}
{p2col :{hi:[R] alpha} {hline 2}}Cronbach's alpha{p_end}
{p2colreset}{...}


{title:Syntax}

{p 8 14 2}
{cmd:alpha}
{varlist}
{ifin}
[{cmd:,} {it:options}]

{synoptset 20 tabbed}
{synopthdr}
{synoptline}
{syntab:Options}
{synopt :{opt a:sis}}take sign of each item as is{p_end}
{synopt :{opt c:asewise}}delete cases with missing values{p_end}
{synopt :{opt d:etail}}list individual interitem correlations and covariances{p_end}
{synopt :{opth g:enerate(newvar)}}save the generated scale in {it:newvar}{p_end}
{synopt :{opt i:tem}}display item-test and item-rest correlations{p_end}
{synopt :{opt l:abel}}include variable labels in output table{p_end}
{synopt :{opt m:in(#)}}must have at least {it:#} observations for inclusion{p_end}
{synopt :{opth r:everse(varlist)}}reverse signs of these variables{p_end}
{synopt :{opt s:td}}standardize items in the scale to mean 0, variance 1{p_end}
{synoptline}
{p2colreset}{...}
{p 4 6 2} {opt by} may be used with {cmd:alpha}; see {help by}.


{title:Description}

{pstd}
{cmd:alpha} computes the interitem correlations or covariances for all
pairs of variables in {it:varlist} and Cronbach's alpha statistic for the
scale formed from them.  At least two variables must be specified with
{cmd:alpha}.  


{title:Options}

{dlgtab:Options}

{phang}{opt asis} specifies that the sense (sign) of each item be taken
as presented in the data.  The default is to determine the sense empirically 
and reverse the scorings for any that enter negatively.

{phang}{opt casewise} specifies that cases with missing values be
deleted listwise.  The default is pairwise computation of
covariances/correlations.

{phang}{opt detail} lists the individual interitem correlations and
covariances.

{phang}{opth generate(newvar)} specifies that the scale constructed
from {it:varlist} be stored in {it:newvar}.  Unless {opt asis} is
specified, the sense of items entering negatively is automatically reversed.
If {opt std} is also specified, the scale is constructed using standardized
(mean 0, variance 1) values of the individual items.  Unlike most Stata
commands, {opt generate()} does not employ casewise deletion.  A score is
created for every observation for which there is a response to at least one
item (one variable in {it:varlist} is not missing).  The summative score is
divided by the number of items over which the sum is calculated.

{phang}{opt item} specifies that item-test and item-rest correlations and the
effects of removing an item from the scale be displayed.  {opt item} is valid
only when more than two variables are specified in {it:varlist}.

{phang}{opt label} requests that the detailed output table be displayed in a
compact format that enables the inclusion of variable labels.

{phang}{opt min(#)} specifies that only cases with at least {it:#}
observations be included in the computations.  {opt casewise} is a shorthand
for {opt min(k)}, where {it:k} is the number of variables in
{it:varlist}.

{phang}{opth reverse(varlist)} specifies that the signs (directions)
of the variables (items) in {it:varlist} be reversed.  Any variables
specified in {opt reverse()} that are not also included in {cmd:alpha}'s
{it:varlist} are ignored.

{phang}{opt std} specifies that the items in the scale be standardized
(mean 0, variance 1) before summing.


{title:Examples}

{phang}{cmd:. alpha q1-q10}

{phang}{cmd:. alpha bg2cost1-bg2cost6 dotest1-dotest6, std}

{phang}{cmd:. alpha bg2cost1-bg2cost6 dotest1-dotest6, std gen(score)}


{title:Also see}

    Manual:  {bf:[R] alpha}

{psee}
Online:  {helpb factor}, {helpb loneway}, {helpb pca}
{p_end}