BEES2041 Lecture Notes - Lecture 2: Exploratory Data Analysis, Variance, Box Plot
9 Jun 2018
School
Course
Professor
Descriptive Statistics
-Describe the nature of distributions
-Do’t deal ith proailities of ay gie outoe
Measures of central tendency:
-Mean Calculation formula
-Median: central value such that Half of the population have Higher Values, Half have lower
Mean & Median are EQUAL in Symmetrical distributions
(aka, Mean & median different in Asymmetrical distributions)
-Mode is most Frequent value of population
-variance of population (calculation formula)
Variance: average differences between data & mean
Sample variance: estimate of population variance
Measures of variation:
Standard deviation of sample returns variation to same units as original variable
-Standard error of mean Measures how much (on average) sample means are expected to
vary if repeatedly sampled from a population
-Coefficient of variation Measures standard deviation (SD) as percentage of mean
Exploratory data analysis
-always visualise data before doing any statistical tests
-help find patterns in data
-necessary to summarise large data sets
-needed to check assumption of statistical tests
One variable :
frequency histograms
box plot
Outliers: extreme values that may strongly influence the graphs / analyses
Always check if they are real (make sure it was not a typo in your spreadsheet)
Two variables:
Continuous Y & categorical X
1 Bar charts of means +/- measures of variances
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