Free Webinars

The Mystery of Nondetects: How Censored Data Methods Work
Sept 24, 2019 10 am Pacific, 1 pm Eastern.
Webinar Registration

Substitution of a constant times the reporting/detection limit (for example 1/2 DL) introduces bias into estimates of mean, standard deviation and upper confidence limits. The better alternative is to use methods for censored data. How these methods work is not widely understood by the environmental science community. The most frequent question I am asked about them is "But what number do I put in for the nondetects when I use them?" The answer is "you don't". The reasons why this is so, and how these methods work, will be presented in this webinar. This is a snapshot of one subject from our new online course "Nondetects And Data Analysis".

Free webinars for your viewing at our Online Training Center . Click the "View All Courses" button to see more than the top 3. The webinars will be listed as free courses.

1. Intro to Nondetects and Data Analysis
An introduction to data analysis for variables with nondetects.
Free. 50 mins.
Materials from the webinar (including slides and info) can also be downloaded as a zip file:
Download here

2. Fitting Distributions to Data with Nondetects
Making the most of small datasets with nondetects.
Free. 50 mins.
Recorded 2/19/2019. Q&A file and pdf of slides also available for download on our
Downloads page.

3. Testing Groups of Data With Multiple DLs
“ANOVA-type” tests and multiple comparison tests with nondetects.
Free. 55 mins.
Recorded 3/19/2019. Q&A file and pdf of slides also available for download on our
Downloads page.

4. The Mystery of Nondetects: How Censored Data Methods Work
Free. 60 mins.
Recorded 5/21/2019 Q&A file and pdf of slides also available for download on our Downloads page.

5. Seven Perilous Errors in Environmental Statistics
Seven common errors to avoid!
Free. About 1 hour.

Seven common errors in statistical analysis by environmental scientists all stem from an outdated understanding of statistics. I'll define the seven 'perilous errors' and how each can be avoided. They revolve around old ideas about hypothesis tests, p-values, using logarithms of data, evaluating what is a good regression equation, evaluating outliers and dealing with nondetects. Understanding why each error is perilous can save the scientist from publishing incorrect statements, using inefficient analysis methods, and wasting scarce financial resources. These errors have persisted through the years -- break the cycle and step into the 21st Century.

6. Intro to R
Break down the barrier of how to get started using R!
Free. About 1 hour.

R is one of the most widely used statistics software packages in the world. Its versatility as a programming language and its interconnectivity with email, web page generation and other computer processes make it a bit daunting for people just starting to use it for data analysis. It need not be that way. This webinar introduces you to R software and its use for data analysis. You'll learn how to type commands, install and load packages, and use the pull-down menus of R Commander (Rcmdr) to compute confidence intervals and a test for whether the mean exceeds a numerical standard.

7. Statistics For Managers
What your employees need to know to stay current with statistical methods today
Free. About 1 hour.

People requested this 2015 webinar be made available for listening. And here it is!
1. Permutation Tests -- what they are and why they are important.
2. Free Software for Environmental Statistics
3. Better Methods for Handling Nondetects
4. Analysis of "real-time", frequently collected data

8. Forty Years of Water Quality Statistics: What's Changed, What Hasn't?
Free. 60 mins.
Some folks are still using methods from the era of black rotary-dial phones. You've upgraded your phone. How about updating your statistical methods?
Materials from the webinar (including slides and info) can be downloaded on the webinar site.

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Past attendees said this about our webinars:
"A great introduction to stuff I need to know, and a great review of things I once knew. You have an uncanny ability to convey things most people avoid into a language people can understand."
……………………… -- State agency staff

"Thanks Dennis, we really enjoyed the seminars and feel they will be very helpful in future data analyses."
………………………-- Environmental consultant
Online at:

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