Recent Comments

    Categories

    The Wilcoxon Sign Rank Test: A Geological Example

    Geological data is often not normally distributed, and with data that is not normally distributed parametric methods should not be used.  In this case, I did a paired experiment, which is a simplified example of blocking, where comparisons are made between similar experimental units. This blocking needs to be done prior to performing the […]

    Univariate Statistics Part 4, Methods to compare distributions

    Comparing Distribution. Chi-square and other robust methods.

    Most of the discussion previously has assumed normal distributions, and given some options for nonparametric situations, but we need tests to determine what type of distribution we are dealing with.

    The chi-square goodness-of-fit test is the first, and simplest way to do this. It compares a […]

    Univariate Statistics Part 3, How do you comparing central tendency

    These are tests used to compare the averages between to distributions. Comparing two means, we could compare the mean to a predefined value (e.g., Are these sandwiches on average different that Subway’s 12” claim?). Or we could compare two means from two separate sample sets together (e.g., Do the sandwiches at this Subway […]

    Univariate Statistics Part 2, measuring scale, and the standard deviation

    Measures of spread and scale

    Often, we may want to compare our sample variance, with a hypothetical population variance, in order to ensure it doesn’t exceed a certain value. Back to our sandwiches, perhaps Subway is okay with footlongs varying in length by no more than 1”. The test statistic we use is […]

    Univariate Statistics Part 1, Formulating your hypothesis, and the p-value

    We often would like to compare a population parameter to our sample. We may know this parameter in advance, or we may want to compare it to another sample. Suppose we want to know for sure Subway is giving us a real footlong sandwich when we ask for one. We buy 30 12″ […]