Stata 9, Summing up

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Stata 9, Summing up
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Why Stata

• Pro
• Aimed at epidemiology
• Many methods, growing
• Graphics
• Structured, Programable
• Comming soon to a course near you
• Con
• Memorygtfile size
• Copy table

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Use

• Import data
• DBMS-Copy
• Do files
• Highlight commands, Ctrl-D
• Full syntax
• by varlist command varlist if exp in
  range , opts
• list if agelt50
• list in 1/10
• regress y x1 x2 if deltabetalt0.3

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Data check

• describe describe dataset
• summarize means
• list x1 x2 in 1/10 list first 10 obs
• gen id_n generate id
• numlabel x1 x2, add add value to label
• tab x1 x2, mis x1 by x2 including missing
• list id x1 if (x2.)(x3.)1 list if x1 or
  x2 is missing
• egen missrowmiss(x1 x2 x3) number missing
• tab miss from 0-3 missing
• drop x1 if x1lt0 drop negative
• drop x1 if x1gt100 x1lt. drop large

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Graphics

• Explore data
• kdensity y distribution
• scatter y x scatter
• twoway (scatter y x)(lfit y x) scatterline
• Plot means
• graph bar (mean) y1 y2 mean of y1 and y2
• graph bar (mean) y, over(c) mean y for values of
  c
• Plot means using aggregate and twoway
• preserve
• collapse (mean) ymy, by(c) one line pr c value
• line ym c lineplot mean(y) by c
• restore

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Help

• General
• help command
• search keyword
• findit keyword
• Examples
• help table
• search GAM
• findit GAM

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Continuous symetrical data

• Univariate
• kdensity y distribution
• summarize y means
• Bivariate
• sdtest y, by(sex) equal variance?
• ttest y, by(sex) equal means?
• oneway y parity3, tabulate equal means?
• Multivariable
• regress y x1 x2 linear regression
• dfbeta

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Some options

• mean y meanci
• mean y, cluster(region)
• mean y, standardize
• mean y, bootstrap

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Continuous skewed data

• Univariate
• kdensity y distribution
• summarize y, detail medians
• Bivariate
• table sex, c(median y) medians
• ranksum y, by(sex) equal medians?
• table sex, c(median y) medians
• kwallis y, by(age3) equal medians?
• Multivariable
• regress y x1 x2 linear regression
• dfbeta

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Categorical data

• Univariate
• tabulate y freq table
• proportion y prop with ci
• Bivariate
• tabulate y sex, col chi2 column , chisquare
• Multivariable
• logistic y x1 x2 logistic regression
• binreg y x1 x2, rd risk difference

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Survival data

• Set
• stset time, failure(status1)
• Univariate
• sts graph, fail gwood KM failureci
• Bivariate
• sts graph, fail by(x1) KM failure
• sts test x1 log rank test
• Multivariable
• stcox x1 x2 cox regression

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Model building

• Estimate
• regress y exp exposure only
• est store m1 store
• regress y exp x1 x2 exposure conf.
• est store m2 store
• Compare
• est table m1 m2 confounding?
• est stat m1 m2 model fit
• Interaction
• regress y exp x1 x1exp with interaction term
• lincom exp2x1exp effect of exp for x12

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Model testing

• Assumptions
• Independent errors discuss
• Linear effects categorize, plot coefs
• Constant error plot resid (linear mod)
• Influence
• Influential points plot delta-beta

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• Regression with simple error structure
• regress linear regression (also heteroschedastic
  errors)
• nl non linear least squares
• GLM
• logistic logistic regression
• poisson Poisson regression
• binreg binary outcome, OR, RR, or RD effect
  measures
• Conditional logistc
• clogit for matched case-control data
• Multiple outcome
• mlogit multinomial logit (not ordered)
• ologit ordered logit
• Regression with complex error structure
• xtmixed linear mixed models
• xtlogit random effect logistic

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GLLAMM

• Generalized Linear Latent And Mixed Models
• Response types
• continuous
• ordered and unordered categories
• counts
• survival
• Model types
• Generalized Linear Models (GLM)
• Structural Equation Models (SEM)
• Mixed Models
• Measurement Error models

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