Survey

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Transcript

Describing Data – Measures of Variability and Spread Goals: • Learn how to describe the spread (or variability) of a data set • Calculate the range, inter-quartile range, variance, and standard deviation • Use technology to make calculations easier CLASS NOTES Questions/Main Ideas Name _________________________________ Date _____________ Measure of spread: The range A statistics class, on the first day, took a poll as to what each student thought their final grade in the course would be. The following data was collected: 76 81 100 100 92 96 80 83 95 100 93 93 82 93 100 70 80 93 Measures of position: Quartiles Interquartile range (IQR) – the “width of the middle 50%” Spread about the median... Variance Consider the following small data set: 3, 7, 10, 12 A typical squared deviation about the mean Standard Deviation A typical deviation about the mean Do I really have to do this by hand? R data <- c(76,81,100,100,92,96,80,83,95,100,93,93,82,93,100,70,80,93) mean(data) median(data) var(data) sd(data) Graphing calculator Stat → Edit (Enter the data) Stat → Calc → 1VarStats library(s20x) data <- c(76,81,100,100,92,96,80,83,95,100,93,93,82,93,100,70,80,93) options(digits=4) summaryStats(data) data <- c(76,81,100,100,92,96,80,83,95,100,93,93,82,93,100,70,80,93) options(digits=3) quantile(data,type=2) Resistant? Consider the following two data sets: Set 1: 1,3,3,5,6,6,9,10 Range IQR Variance Standard deviation Set 2: 1,3,3,5,6,6,9,10,250