Statistical Analysis

Learning Dunnett’s Test: A Post-Hoc Analysis in R for Comparing to a Control Group

When conducting complex statistical analyses, particularly those involving comparisons among multiple group means, researchers often rely on the ANOVA (Analysis of Variance) framework. However, a significant result from an ANOVA only indicates that at least two groups differ; it does not specify which pairs are responsible for that difference. This necessitates a subsequent procedure known […]

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Learning to Visualize Interactions: A Guide to Creating Interaction Plots in R for Two-Way ANOVA

Understanding Interaction Effects in Statistical Modeling The two-way ANOVA is a powerful statistical technique utilized to assess whether the means of a continuous outcome variable differ across groups defined by two distinct categorical factors. This method allows researchers to simultaneously evaluate the independent effects of each factor, known as main effects, and the joint effect

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Learning to Calculate Area Under the Standard Normal Curve Using the Z-Table

The Fundamental Challenge: Navigating the Normal Distribution A cornerstone concept in elementary statistics involves calculating probabilities associated with the Standard Normal Curve. This curve, often referred to as the Z-distribution, is essential because it allows us to standardize and compare data from various sources. The most frequently posed challenge to students is: “Find the indicated

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Perform Dunn’s Test in R

Understanding Non-Parametric Post-Hoc Analysis When researchers need to compare the central tendencies of three or more independent groups, the standard approach is often the One-Way ANOVA. However, this parametric test relies on strict assumptions, notably that the data within each group are normally distributed and that the variances are homogeneous. When these assumptions are violated,

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Perform Dunn’s Test in Python

A Kruskal-Wallis test is used to determine whether or not there is a statistically significant difference between the medians of three or more independent groups. It is considered to be the non-parametric equivalent of the One-Way ANOVA. If the results of a Kruskal-Wallis test are statistically significant, then it’s appropriate to conduct Dunn’s Test to determine exactly which groups are

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Calculate Point-Biserial Correlation in Excel

Point-biserial correlation is used to measure the relationship between a binary variable, x, and a continuous variable, y. Similar to the Pearson correlation coefficient, the point-biserial correlation coefficient takes on a value between -1 and 1 where: -1 indicates a perfectly negative correlation between two variables 0 indicates no correlation between two variables 1 indicates a perfectly positive

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Make a Box Plot in Google Sheets

A box plot, often referred to as a box-and-whisker plot, is a powerful tool in exploratory data analysis. Its primary function is to visually display the distribution of a dataset based on its five number summary. This summary provides a concise statistical snapshot of the data’s spread, skewness, and central location. Understanding these five key

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Calculate Skewness & Kurtosis in Google Sheets

In the field of statistics, understanding the inherent shape of data is crucial for accurate analysis. Two fundamental measures used to quantify the form of a probability distribution are skewness and kurtosis. Together, these metrics provide essential insights beyond central tendency (mean, median, mode) and variability. This comprehensive tutorial will explain the theoretical foundations of

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Calculate Standard Error of the Mean in Google Sheets

The standard error of the mean (SEM) is a fundamental statistical metric used to quantify the precision of a sample mean as an estimate of the true population mean. While the standard deviation measures the dispersion of individual data points around the sample mean, the SEM specifically addresses the variability between the sample mean and

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Create a Covariance Matrix in Google Sheets

Understanding Covariance: The Foundation of Relationship Measurement In the realm of statistics and data science, Covariance stands as a foundational metric essential for quantifying the linear relationship between two random variables. Essentially, it serves as a measure of how two different variables fluctuate together. When two variables exhibit a strong positive covariance, it indicates that

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