Data analytics, statistics, and more

Exploratory Spatial Data Analysis and Kriging in R

This post presents and demonstrates several methods for exploratory spatial data analysis using the R language for statistical computing and visualization. These methods can be used for identifying spatial dependence patterns and spatial heterogeneity, which are critical components of variogram development and the kriging procedure.

May 29, 2023

Natural Neighbor Interpolation With R

This post presents and demonstrates several methods for natural neighbor interpolation using the R language for statistical computing and visualization. The results are compared to those obtain using ordinary kriging.

May 22, 2023

Calculation of 95% Upper Confidence Limit for Left-Censored Data

This post presents methods that can be used to calculate a 95% upper confidence limit on the mean of an unknown population for left-censored data sets (i.e., containing a mixture of detects and non-detects). The preferred approach depends on many factors, including the number of samples and the distributional shape of the data.

May 10, 2023

Sample Size Determination for Correlation Studies

Determination of an appropriate sample size when performing a correlation sudy is usually based on achieving sufficient power that the test can reject the null hypothesis that the correlation is zero. Sample sizes found using this method can yield confidence intervals that are so wide that they provide very little useful information about the magnitude of the correlation. An alternative approach is to choose a sample size that achieves a sufficiently narrow confidence interval for measuring the smallest correlation of potential interest.

March 25, 2023

Statistical Power of Two-Sample Central Tendency Tests with Unequal Sample Size

Two-sample hypothesis tests are used to compare the means, medians, or other percentiles of two populations to determine if there is a significant difference between the groups. For a given total sample size, statistical power is maximized if the sample sizes for each group are equal. With highly unequal group sizes, each additional observation adds little additional resolution. This simulation study focuses on determining the effect of unequal sample sizes on the statistical power of two-sample hypothesis tests, assuming independent samples with equal variance.

January 3, 2023