# Technical Studies Reference

### Study Subgraph Standard Deviation

This study calculates the Standard Deviation of the selected study Subgraph over the length specified by the Standard Deviation Length Input. To select the study to use,set the Based On study setting to select the study and set the Input Data Input to the specific study Subgraph.

Let $$X$$ be a random variable denoting the Input Data Input, and let $$X_t$$ be the value of the Input Data at Index $$t$$. Let the Standard Deviation Length and Standard Deviation Multiplier Inputs be denoted as $$n$$ and $$k$$, respectively. Then the displayed values of Study Subgraph Standard Deviation at Index $$t$$ are given by $$X_t$$ for $$t < n$$, and by $$X_t \pm k \cdot \sigma_t(X,n)$$ for $$t \geq n$$.

More than likely you will want to display this study in the same chart region as the study that it is based on. To do this, set the Chart Region setting in the Study Settings window for this study to the same Chart Region as the study you have based it on using the Based On setting. You can also hide the study you have based this study on by opening the Study Settings window for that other study and enabling the Hide Study option.