R Statistical Software Basics – Descriptive Statistics - Variance

The practice sheet titled StatisticMarks Data.csv downloaded from Link. – Download Sheet

About the Data Sheet - The data in this sheet is related to marks scored by 100 Students in a Statistical Test.

Based on the data, we will use R Software Statistical functions to analyze the descriptive statistics.

In the Data Sheet, we have Data from A2:A101, A1 being the header of the Data. I have stored the StatisticMarks.csv file in Working Directory on my Desktop.

setwd("C:/Users/Rajesh Prabhakar/Desktop/R")

For inputting or reading Data from “StatisticMarks.csv” file, R Command would be

StatMarks=read.csv("StatisticMarks.csv")

Variance

Variance (σ²) is a measure of the dispersion of a set of data points around their mean value.

In other words, variance is a mathematical expectation of the average squared deviations from the mean.

It is computed by finding the probability-weighted average of squared deviations from the expected value. Variance measures the variability from an average (volatility).

In R Statistical Software, Variance is represented by function “var”.

var(  )

In the Data Sheet, we have Data from A2:A101, A1 being the header of the Data titled StatisticsMarks. 

var(StatMarks$StatisticsMarks)

StatMarks is the name of the variable in which we stored the data followed by $ sign and column header of the Data i.e. StatisticsMarks.

Remember the title of the column should be exactly same including the large caps & small caps or else it will give error.

In R the file names, column headers and row headers should exactly match the same or else the function will give errors

The result of this function in R Console is

var(StatMarks)

                StatisticsMarks

StatisticsMarks        202.7777