Blog Archives

Checking for Normality with Quantile Ranges and the Standard Deviation

Checking for Normality with Quantile Ranges and the Standard Deviation

Introduction I was reading Michael Trosset’s “An Introduction to Statistical Inference and Its Applications with R”, and I learned a basic but interesting fact about the normal distribution’s interquartile range and standard deviation that I had not learned before.  This turns out to be a good way to check for normality in a data set.

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Estimating the Decay Rate and the Half-Life of DDT in Trout – Applying Simple Linear Regression with Logarithmic Transformation

Estimating the Decay Rate and the Half-Life of DDT in Trout – Applying Simple Linear Regression with Logarithmic Transformation

This blog post uses a function and a script written in R that were displayed in an earlier blog post. Introduction This is the second of a series of blog posts about simple linear regression; the first was written recently on some conceptual nuances and subtleties about this model.  In this blog post, I will use

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My Own R Function and Script for Simple Linear Regression – An Illustration with Exponential Decay of DDT in Trout

My Own R Function and Script for Simple Linear Regression – An Illustration with Exponential Decay of DDT in Trout

Here is the function that I wrote for doing simple linear regression, as alluded to in my blog post about simple linear regression on log-transformed data on the decay of DDT concentration in trout in Lake Michigan.  My goal was to replicate the 4 columns of the output from applying summary() to the output of lm().

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Discovering Argon with the 2-Sample t-Test

Discovering Argon with the 2-Sample t-Test

I learned about Lord Rayleigh’s discovery of argon in my 2nd-year analytical chemistry class while reading “Quantitative Chemical Analysis” by Daniel Harris.  (William Ramsay was also responsible for this discovery.)  This is one of my favourite stories in chemistry; it illustrates how diligence in measurement can lead to an elegant and surprising discovery.  I find

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Adding Labels to Points in a Scatter Plot in R

Adding Labels to Points in a Scatter Plot in R

What’s the Scatter? A scatter plot displays the values of 2 variables for a set of data, and it is a very useful way to visualize data during exploratory data analysis, especially (though not exclusively) when you are interested in the relationship between a predictor variable and a target variable.  Sometimes, such data come with categorical

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Getting Help with R Programming: Useful Survival Skills

Getting Help with R Programming: Useful Survival Skills

Useful Resources to Learn about R on the Internet When I program in R and struggle with something, the first thing that I usually turn to is Google.  I search the relevant function or the desired outcome, and I often find the solutions within the first few hits.  They likely show up in the documentation,

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Displaying Isotopic Abundance Percentages with Bar Charts and Pie Charts

Displaying Isotopic Abundance Percentages with Bar Charts and Pie Charts

The Structure of an Atom An atom consists of a nucleus at the centre and electrons moving around it.  The nucleus contains a mixture of protons and neutrons.  For most purposes in chemistry, the two most important properties about these 3 types of particles are their masses and charges.  In terms of charge, protons are

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