Blog Archives

Example 8.36: Quadratic equation with real roots

April 29, 2011
By
Example 8.36: Quadratic equation with real roots

We often simulate data in SAS or R to confirm analytical results. For example, consider the following problem from the excellent text by Rice:Let U1, U2, and U3 be independent random variables uniform on . What is the probability that the roots...

Read more »

Example 8.34: lack of robustness of t test with small n

April 12, 2011
By
Example 8.34: lack of robustness of t test with small n

Tim Hesterberg has effectively argued for a larger role for resampling based inference in introductory statistics courses (and statistical practice more generally). While the Central Limit Theorem is a glorious result, and the Student t-test remarkabl...

Read more »

Example 8.28: should we buy snowstorm insurance?

February 28, 2011
By
Example 8.28: should we buy snowstorm insurance?

It's been a long winter so far in New England, with many a snow storm. In this entry, we consider a simulation to complement the analytic solution for a probability problem concerning snow. Consider a company that buys a policy to insure its revenue ...

Read more »

Example 8.27: using regular expressions to read data with variable number of words in a field

February 25, 2011
By
Example 8.27: using regular expressions to read data with variable number of words in a field

A more or less anonymous reader commented on our last post, where we were reading data from a file with a varying number of fields. The format of the file was:1 Las Vegas, NV --- 53.3 --- --- 12 Sacramento, CA --- 42.3 --- --- 2The complication in the...

Read more »

Example 8.26: reading data with variable number of words in a field

February 22, 2011
By
Example 8.26: reading data with variable number of words in a field

A student came with a question about how to snag data from a PDF report for analysis. Once she'd copied things her text file looked like:1 Las Vegas, NV --- 53.3 --- --- 12 Sacramento, CA --- 42.3 --- --- 23 Miami, FL --- 41.8 --- --- 34 Tucson, AZ --...

Read more »

Example 8.25: more latent class models (plus a graphical display)

February 15, 2011
By
Example 8.25: more latent class models (plus a graphical display)

In recent entries (here, here, here and here), we've been fitting a series of latent class models using SAS and R. One of the most commonly used and powerful package for latent class model estimation is Mplus. In this entry, we demonstrate how to use...

Read more »

Example 8.24: MplusAutomation and Mplus

February 7, 2011
By
Example 8.24: MplusAutomation and Mplus

In recent entries (here, here, and here), we've been fitting a series of latent class models using SAS and R. One of the most commonly used and powerful software package for latent class model estimation is Mplus. This commercial software includes su...

Read more »

Example 8.23: Expanding latent class model results

January 31, 2011
By
Example 8.23: Expanding latent class model results

In Example 8.21 we described how to fit a latent class model to data from the HELP dataset using SAS and R (using poLCA(), and then followed up in example 8.22 using randomLCA(). In both entries, we classified subjects based on their observed (manifes...

Read more »

Example 8.22: latent class modeling using randomLCA

January 24, 2011
By
Example 8.22: latent class modeling using randomLCA

In Example 8.21 we described how to fit a latent class model to data from the HELP dataset using SAS and R. Subjects were classified based on their observed (manifest) status on the following variables (on street or in shelter in past 180 days [homele...

Read more »

Example 8.21: latent class analysis

January 18, 2011
By
Example 8.21: latent class analysis

Latent class analysis is a technique used to classify observations based on patterns of categorical responses. Collins and Lanza's book,"Latent Class and Latent Transition Analysis," provides a readable introduction, while the UCLA ATS center has an o...

Read more »