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Clojure for Data Science

You're reading from   Clojure for Data Science Statistics, big data, and machine learning for Clojure programmers

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Product type Paperback
Published in Sep 2015
Publisher
ISBN-13 9781784397180
Length 608 pages
Edition 1st Edition
Languages
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Author (1):
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Henry Garner Henry Garner
Author Profile Icon Henry Garner
Henry Garner
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Table of Contents (12) Chapters Close

Preface 1. Statistics FREE CHAPTER 2. Inference 3. Correlation 4. Classification 5. Big Data 6. Clustering 7. Recommender Systems 8. Network Analysis 9. Time Series 10. Visualization Index

Standard error


While the standard deviation measures the amount of variation there is within a sample, the standard error measures the amount of variation there is between the means of samples taken from the same population.

Note

The standard error is the standard deviation of the distribution of the sample means.

We have calculated the standard error of dwell time empirically by looking at the previous 6 months of data. But there is an equation that allows us to calculate it from only a single sample:

Here, σx is the standard deviation and n is the sample size. This is unlike the descriptive statistics that we studied in the previous chapter. While they described a single sample, the standard error attempts to describe a property of samples in general—the amount of variation in the sample means that variations can be expected for samples of a given size:

(defn standard-deviation [xs]
  (Math/sqrt (variance xs)))

(defn standard-error [xs]
  (/ (standard-deviation xs)
     (Math/sqrt (count xs...
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