Jan. 3, 2021

Cengiz Zopluoglu

multidimensional IRT

item response theory

R

numerical integration

2021

This post provides R code to use numerical integration for calculating population-level mean and covariances between item scores generated based on the compensatory and partially compensatory multidimensional models.

Dec. 8, 2020

Cengiz Zopluoglu

dimensionality

DETECT

multidimensional IRT

item response theory

R

2020

The post is organized as follows. First, we simulate a dataset using a multidimensional IRT model and compute the actual DETECT value using the correct item partitioning. Second, a brief description of the DETECT index is provided, and the DETECT value is calculated based on this definition based on the true item clustering for the simulated dataset. Then, we compute the same value using the original DETECT program by executing it through R. Finally, we conduct a simple simulation to demonstrate how to automate running DETECT to analyze many datasets and processing the DETECT output files in R.

May 5, 2020

Cengiz Zopluoglu

item response theory

continuous response model

equating

R

2020

A non-peer reviewed opinion about how one can equate oral reading fluency scores from two reading passages with different difficulty levels using Samejima's Continuous Response Model.

March 28, 2020

Cengiz Zopluoglu

2020

web scraping

covid19

A Shiny app is designed to track the number of deceased individuals from 11 major cities in Turkey by scraping data from www.turkiye.gov.tr. By using this Shiny app, you can compare the number of deceased individuals for any given day or date range in 2020 to the number of deceased individuals in the past 10 years on the same day or same date range.

Feb. 26, 2020

Cengiz Zopluoglu

2020

item response theory

graded response model

The interpretation of between-category thresholds in the Graded Response Model is different than the step difficulty parameters in the RSM/PCM/GPCM family due to a different functional form. While the step parameters in the RSM/PCM/GPCM family represent the point on the latent trait continuum where one category becomes more likely than the previous category, it is not the same for between-category thresholds in the Graded Response Model. So, this post is my response to a curious student who wondered at what point on the latent trait continuum the intersections occur between two adjacent categories for the Graded Response Model.

Jan. 7, 2020

Cengiz Zopluoglu

2019

Shiny app

Dec. 31, 2019

Cengiz Zopluoglu

item response theory

continuous response model

Stan

R

2019

I pitched the idea of using Samejima's Continuous Response Model (CRM) to measure the Oral Reading Fluency (ORF) a while ago when I published a paper in 2012. In that paper, I used an ORF dataset from the Minneapolis Public Schools District (MPS) as a real data example. Since then, I don't think anybody has bought the idea of using CRM to measure ORF, so here I am trying one more time with some accessible R code.

Dec. 15, 2019

Cengiz Zopluoglu

item response theory

hyperbolic cosine model

Stan

R

2019

In this post, I do a quick exercise on fitting the hyperbolic cosine model using Stan. The information about this model can be found in Andrich & Luo (1993). The most interesting part is an "Aha!" moment when I discover the bimodality of posterior distribution due to lack of directional constrain.

May 24, 2019

Cengiz Zopluoglu

web scraping

R

elections

Turkish elections

2019

A while ago, I compiled the election data for the 2019 mayoral elections in Turkey, which took place on March 31, 2019, through the Anadolu Agency website, only accessible information back then because the website for the Turkey's Higher Electoral Commission (YSK) was down and they did not make the official election data available until recently. This data was also limited as the Anadolu Agency only provided overall numbers (not for each ballot box). Now, it seems that YSK's website is alive back again and provides a nice-user friendly dashboard for the election data at the ballot box level. However, their dashboard is not very data-analyst friendly for those who has been starving for a more deeper analysis. Here, I provide the data and the R code I used to scrap this data from YSK's website.

April 18, 2019

Cengiz Zopluoglu

XGBoost

R

item preknowledge

2019

This post includes supplemental material to reproduce the real data analysis presented in the recently published EPM paper.

April 5, 2019

Cengiz Zopluoglu

web scraping

R

elections

Turkish elections

2019

A friend of mine, Dr. Abdullah Aydogan (https://twitter.com/abdaydgn), has asked me this morning if it is possible to pull the data for the 2019 local elections in Turkey. The only accessible information is through the Anadolu Agency (https://www.aa.com.tr/en) because the official election organization's website (http://www.ysk.gov.tr/) has not been working for a while. Here, I provide the code I used to scrap data from the Anadolu Agency, only available source for election results.

April 1, 2019

Cengiz Zopluoglu

web scraping

R

2019

What are the most commonly used keywords in published articles in educational measurement journals? Is there any trending topic in educational measurement journals? I decided to do a sample analysis in the context of Educational and Psychological Measurement (EPM). However, I had figure out first how to compile a dataset of keywords used in EPM. It turned out to be another web scraping story.

Jan. 15, 2019

Cengiz Zopluoglu

XGBoost

R

2019

In one of the working papers under review, I am using the Extreme Gradient Boosting (XGBoost) to identify examinees with potential item preknowledge in a certification exam. In the original paper, one of the reviewers asked more description of the XGBoost to help readers get a conceptual understanding of how XGBoost works. After spending a few weeks on the original paper, I finally felt that I had a good grasp of it. In this post, I provide an informal introduction of XGboost using an illustration with accompanying R code.

Nov. 16, 2018

Cengiz Zopluoglu

elections

US elections

R

2018

Using the elections 2018 data, I practiced how to create a map for an outcome variable,

Nov. 12, 2018

Cengiz Zopluoglu

elections

US elections

R

2018

Some quick insights about 2018 elections

Nov. 7, 2018

Cengiz Zopluoglu

web scraping

R

elections

US elections

2018

This post includes some follow-up R code to scrap 2018 election data from New York Times webpage.

Nov. 6, 2018

Cengiz Zopluoglu

web scraping

R

elections

US elections

2018

This post includes some R code to scrap 2014 election data from New York Times webpage.

- Articles (17)
- 2018 (4)
- 2019 (8)
- 2020 (4)
- 2021 (1)
- continuous response model (2)
- covid19 (1)
- DETECT (1)
- dimensionality (1)
- elections (6)
- equating (1)
- graded response model (1)
- hyperbolic cosine model (1)
- item preknowledge (1)
- item response theory (6)
- multidimensional IRT (2)
- numerical integration (1)
- R (14)
- Stan (2)
- Turkish elections (2)
- US elections (4)
- web scraping (6)
- XGBoost (2)