Statistics How To

RCTs > Blinding in Statistics What is Blinding in Statistics? In medical trials, the term blinding, or double-blind, usually refers to the practice of keeping patients in the dark as to whether they receive a placebo or not. It can also refer to allocation concealment, which is used to avoid selection bias. Double-blind vs. Blinding … Read more

Microsoft Excel for statistics > Hypothesis Test in Excel #1 Note: This article covers z-tests in Excel. If you have a small sample (under 30), or don’t know the population standard deviation, run a T Test in Excel instead. Hypothesis Test in Excel: Overview Excel contains a statistical package where you can calculate a range … Read more

Statistics Definitions > Decile Deciles break up a set of data into tenths. They are similar to quartiles. But while quartiles sort data into four quarters, data is instead sorted into ten equal parts: The 10th, 20th, 30th, 40th, 50th, 60th, 70th, 80th, 90th and 100th percentiles.   A decile rank assigns a number to … Read more

Descriptive Statistics > A back to back stemplot is a graphical way to display statistical data. What is a Stemplot? A stemplot is similar to a histogram—it is a tool to help you visualize the shape of a distribution. They have been a common tool for displaying data since the 1970s. With a regular stemplot, … Read more

Statistics Definitions > Yates Correction The Yates correction is made to account for the fact that both Pearson’s chi-square test and McNemar’s test are biased upwards for a 2 x 2 contingency table. An upwards bias tends to make results larger than they should be. If you are creating a 2 x 2 contingency table … Read more

Statistics Definitions > Stanine Score What is a Stanine Score? A stanine (“standard nine”) score is a way to scale scores on a nine-point scale. It can be used to convert any test score to a single-digit score. Like z-scores and t-scores, stanines are a way to assign a number to a member of a … Read more

Statistics Definitions > Goodness of Fit Tests The goodness of fit test is it tells you if your sample data represents the data you would expect to find in the actual population. More specifically, it is used to test if sample data fits a distribution from a certain population (i.e. a population with a normal … Read more

Box Plots > Parallel boxplots (or parallel box-and-whisker plots) are a comparison between of two or more five-number summaries. The five number summary is a set of statistics: The Median The Lower Quartile The Upper Quartile The Minimum The Maximum The summaries for each data set are both plotted on the same graph for easier … Read more

Probability > Hoeffding’s inequality is useful for bounding quantities that are hard to compute. It gives an upper bound on the probability that the sum of a set of random variables deviates from the expected value. In layman’s terms, lets say we have a set of variables. When we find the average, we should usually … Read more

Statistics Definitions > A frequency in statistics is the number of times an event or observation happened in an experiment or study. It can also be defined simply as a count of a certain event. For example, you might conduct a survey of pet owners to see how many people owned certain kinds of pets. … Read more