Stata exercises solutions

Stata is the most popular program for statistical analysis at the SSCC, as it is extremely powerful and relatively easy to learn. Its straightforward but flexible syntax makes it a good choice for data management, and it implements a very large number of statistical techniques.

Stata also has a an extensive user community which has made a great deal of code available, including many additional estimators. The goal of Stata for Researchers as opposed to Stata for Students is to give you a solid foundation that you can build on to become an expert Stata user.

If your goal is to learn just enough Stata to get you through a particular course you should probably read Stata for Students instead. There are two different approaches one can take to Stata. One is to use it as an interactive tool: you start Stata, load your data, and start typing or clicking on commands. This can be a good way to explore your data, figure out what you want to do, and check that your programs worked properly.

It can also be useful when you're trying to figure out something new because you get immediate feedback.

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However, interactive work cannot be easily or reliably replicated, or modified if you change your mind. It's also very difficult to recover from mistakes—there's no "undo" command in Stata.

The other approach is to treat Stata as a programming language. In this approach you write your programs, called do files, and run them when they're complete.

A do file contains the same commands you'd type in interactive Stata, but since they're written in a permanent file they can be debugged or modified and then rerun at will.

They also serve as an exact record of how you obtained your results—a lab notebook for the social scientist. Any work you intend to publish or present should be done using do files.

Thus this series will for the most part ignore Stata's graphical user interface and prepare you to write do files for research. Some of the articles in this series use example files.

Alternatively, you can download a zip file containing all the example files. Each topic includes exercises, and solutions are given for most of them. While many of the exercises are short questions to test your understanding of the material, others require more work and are designed to give you experience working with Stata.

If you are currently involved in a research project it may be a better use of your time to get your Stata experience by working on your project. If you get stuck on an exercise it's probably best to move on.

stata exercises solutions

On the other hand, you can learn from reading the solutions even if you don't do all the exercises. Stata looks and acts the same whether it's running on Windows or Linux or on a Mac.

Running Stata jobs on Linstat is probably easier than you think: read Using Linstat to learn how. Stata for Researchers: Introduction Stata is the most popular program for statistical analysis at the SSCC, as it is extremely powerful and relatively easy to learn. Windows vs. Linux Stata looks and acts the same whether it's running on Windows or Linux or on a Mac. Contact Us RSS.Why Stata?

Supported platforms. Stata Press books Books on Stata Books on statistics. Policy Contact. Bookstore Stata Journal Stata News. Contact us Hours of operation. Advanced search. Buy from Amazon As an Amazon Associate, StataCorp earns a small referral credit from qualifying purchases made from affiliate links on our site.

Amazon Associate affiliate link. Bookshelf is free and allows you to access your Stata Press eBook from your computer, smartphone, tablet, or eReader.

Enter your eBook code. Your eBook code will be in your order confirmation email under the eBook's title. You may then download Bookshelf on other devices and sync your library to view the eBook.

Bookshelf is available on the following:. Download Bookshelf software to your desktop so you can view your eBooks with or without Internet access. Download the Bookshelf mobile app from the Itunes Store. Android Bookshelf is available for Android phones and tablets running 4.

Download the Bookshelf mobile app from the Google Play Store. Mac Bookshelf is available for macOS X Bookshelf allows you to have 2 computers and 2 mobile devices activated at any given time.Unit Exercise 1. Unit Exercise 2.

Unit exercise 3. Unit exercise 7. Please click here. You can also visit our following web pages on different stuff in math. Variables and constants. Writing and evaluating expressions. Solving linear equations using elimination method. Solving linear equations using substitution method. Solving linear equations using cross multiplication method. Solving one step equations. Solving quadratic equations by factoring.

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Solving quadratic equations by quadratic formula. Solving quadratic equations by completing square. Nature of the roots of a quadratic equations. Sum and product of the roots of a quadratic equations. Algebraic identities. Solving absolute value equations.

stata exercises solutions

Solving Absolute value inequalities. Graphing absolute value equations. Combining like terms. Square root of polynomials. Remainder theorem. Synthetic division. Logarithmic problems. Simplifying radical expression. Comparing surds.Why Stata? Supported platforms. Stata Press books Books on Stata Books on statistics. Policy Contact. Bookstore Stata Journal Stata News. Contact us Hours of operation. Advanced search. Some of these resources are based on earlier versions of Stata.

These are also useful for users of Stata 16, because Stata preserves features from earlier versions. Because Stata is cross-platform compatible, even if tutorials claim to require a particular operating system, they will be applicable to all platforms; only the default directories and path specifications will be different.

stata exercises solutions

Stata: Data Analysis and Statistical Software. Go Stata. Purchase Products Training Support Company. Topics start from basic Stata usage, and progress through common data management tasks through to using Stata for a wide variety of analysis topics.

There are also some nice notes about fitting generalized linear models using Stata.

stata exercises solutions

Stata cheat sheetsDr. Tim Essam and Dr. Laura Hughes, USA These compact yet well-organized sheets cover everything you need, from syntax and data processing to plotting and programming, making them handy references to download for quick use. Don't miss the Stata Web Books. In particular, there are some good pointers on interpreting predictive margins and marginal effects.

New users may want to visit the Getting Started with Stata page. Multilevel ModellingCenter for Multilevel Modelling, University of Bristol, UK There approximately pages of materials covering fitting multilevel models for continuous and binary dependent variables in Stata using the xtmixed and xtmelogit commands.

Users have to register to access the pdfs, datasets and do-files, but all materials are made freely available.There are 10, observations of 59 variables.

Stata: Data Analysis and Statistical Software

The full describe output is suppressed for space, but you should run it. Blood pressure is highly correlated, more-so than height and weight. Weight is also correlated with both forms of BP. Height looks to be completely independent of boood pressure.

We can see the correlation between blood pressure measures, with a bit stronger of a relationship for men. We can look at the rowwise percents. The F-test rejects so the model is informative. If you look at a histogram for lead. We see right skew. The maintainers of this data noticed the same concern, as they include a loglead variable in the data to attempt to address this. Nothing of concern here. The p-value is very small, so it is statistically significant.

However, if we look at lead levels:. We see that lead levels range from 2 to The coefficient on age is about. Unlikely to be clinically interesting! This is a side effect of the massive sample size.

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It looks like South is significantly lower levels of lead than the other regions, which show no difference between them. We see significance in the interaction, so we looked at the margins.

Activity 1 - Exercise 1 computing a new variable in Stata

It looks like men show a slight decline in lead as age increases again, rescaling. The marginal plot helps us to visualize this. For men, from age 20 to 70, the average lead decreases barely half a point.

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For women, we see nearly a 3 point average increase. We cannot reject the model fit even once we switch to the proper Hosmer-Lemeshow test, which used 20 instead of 10 because we have 10 predictors. Blacks are more likely to have diabetes than whites or others. Age and weight are positive predictors whereas height is a negative predictor for some reason.

There is no effect of gender or region. The estimated random variance is non-zero, so yes, the random effects for restaurants are warranted. We could just run correlatebut the postestimation commands following mean are fairly limited, so bare with me here.

Postestimation commands following models are much more interesting! However, correlation is especially susceptible to this issue. This is by the central limit theorem. Named not for students in a class, but the pseudonym for statistician William Sealy Gosset. This requires the assumption that the ordinal variable can be well approximated by a continuous variable. A t-test assumes we need to estimate the variance as well.

A Z-test assumes we know the variance, which will be more efficient. There are variations of regression with multiple outcomes, but they are for very specialized circumstances and can generally be fit as several basic regression models instead.Chapter 2 was perhaps the most difficult chapter to write because I wanted to cover the creation of Stata programs for the calculation of the log posterior before I had introduced the simulation algorithms that make use of those programs.

As a result some of the applications are a little artificial. The exercises at the end of the chapter are relatively straight forward, none the less they raise some interesting issues. The questions, code and comments should really be viewed alongside one another. This question re-analyses some old data from an early breast cancer screening program. One of the trickiest aspects of the question is to assess your prior for the all-cause death rate perwomen per year in unscreened women.

The downloadable code includes three ways of calculating the posterior. Here is the posterior superimposed on my prior and the likelihood normalized so that it displays conveniently on the same axes.

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We can see that the prior has had little impact on the posterior. In a group exercise I would also superimpose all of the posteriors on the same plot in order to emphasise that the posteriors are much more similar than the priors.

For the screened group I opted for a G 55,10 prior to reflect my belief that screening would be beneficial.

The method for calculating the corresponding posterior is identical to that used for the control group. Plotting the two posterior distributions on the same graph suggests a benefit due to screening much as I anticipated.

It is interesting to distinguish two questions a What is my best guess at the difference in mortality due to screening? This analysis has addressed the first of these questions and the answer rightly depends on the HIPS study data plus everything else I believe about breast cancer screening.

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The second question is different and would require us to strip away my anticipated benefit and to consider only the evidence from the HIPS data. This can be done within a Bayesian context but it requires the calculation of a Bayes Factor and that is not covered until Chapter Is screening beneficial? This question performs a meta-analysis of seven clinical trials.

To give us a feel for the data here is forest plot based on frequentist estimates and confidence intervals. The question requires us to start by setting a prior.

This led me to a rather conservative prior of N Calculation uses a program for calculating the log posterior and is shown in the pdf. My posterior and prior dashed for theta are.

Clearly my prior is consistent with the data.

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It is interesting to represent these distributions on the relative risk RR scale note the Jacobian in the calculations.To browse Academia. Skip to main content. Log In Sign Up. Davie Lee.

Simon, published by Oxford University Press, edition. Please do everyone a favor and do not circulate these solutions. Do not post these solutions on your website.

Stata: Data Analysis and Statistical Software

Do not put them on Russian websites. Do not copy them and hand them out to students. While there is no way for me to enforce these reasonable rules, be assured that I, being a professor at Hogwarts, am in possession of powerful hexes which I have used to protect the secrecy of these solutions.

Those who attempt to circulate these solutions unlawfully will activate the hex and will suffer thirty years of bad luck, including spiders crawling into your underwear.

Some of these solutions have been tested through use in several years of courses. Other solutions have not been completely tested. Errors or ambiguities that are discovered in the exercises will be listed on my web page. If you think you have found errors in the problems or the solutions please do let me know, and I will make sure to fix them in the next version.

Doing so will undoubtedly improve your Karma. Consider a three dimensional simple harmonic oscilla- b Quantum Einstein Solid: tor with mass m and spring constant k i. The full derivation goes as follows. The fact that the T 3 fit is not perfect is a reflection of a that Debye theory is just an approximation in particular that phonons have a nonlinear spectrum!

Note that at low enough Tthe T 3 scaling does indeed work. Find K in perature. If you are brave you can try to evaluate the integral, You will need to leave your answer in terms of an inte- but you will need to leave your result in terms of the gral that one cannot do analytically. Riemann zeta function. In 2d there should be 2N modes. Assume longitudinal and transverse sound velocities are equal. You might not guess the ones with the abso- Physicists should be good at making educated guesses: lutely highest or lowest temperatures, but you should be Guess the element with the highest Debye temperature.

Diamond is the obvious guess and indeed Argon 92 K it does have the highest Debye temperature. The Krypton 64 K lowest is harder to guess. One presumably wants a soft material of some Xenon 64 K sort — also possibly a heavy material.

Radon 64 K Soft and heavy metals like mercury are good guesses. Also good guesses are Noble gases where the Rubidium 56 K spring constant is very low weak interaction between the atoms. Also Cesium 32 K heavy soft group 1 metals are good guesses.

Why does it not quite match the result From Fig. Debye theory predicts the heat capacity at all possible temperatures. The Debye temperature quoted in the text is chosen so as to give a good fit over the full temperature range.

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