Statistics is a branch of mathematics. It consists of tools and techniques that help describe, organize and interpret information or data.* There are a couple of ways to do this:

Descriptive Statistics summarizes or describes data characteristics in a meaningful way. In general, there are two ways in which this data is usually described: Measures of central tendency (e.g. mode, median, mean) or Measures of spread (e.g. range, quartiles, standard deviation)

Inferential Statistics draws conclustions (predictions) from population samples to make generalizations about the entire population

The Oregon Tech Libraries offer several books that can help you with statistics. Many of these books employ various tooks to help them in analyzing data such as R, Python, SPSS, and Tableau. However, the general principles will be the same for any tool you use.

Karen Kunz

What is Statistics
Intoduction to Statistics
Descriptive vs Inferential Statistics
Descriptive Statistics definitions
Central Tendencies
(an estimate of the "center" of a distribution of values)

Median: The "middle" of a sorted list of numbers
  • Found by ordering the numbers and finding the middle number
  • When the list of numbers is even, the 2 middle numbers are averaged for the median
  • Also known as the 50th percentile
Mean: Same as what most people call average.
  • Found by adding up a list of numbers and dividing by the count of numbers in the list
Mode: The most commonly occuring value
  • Found by counting those numbers that repeat
  • Those that repeat the most are the "mode"
  • There may be more than one "mode"
  • There may be no mode
(spread of the values around the central tendency)

Standard Deviation: extent of deviation for a group as a whole 
  • Find the Mean
  • Subtract the mean from the value of each item
  • Square the result
  • When finished, sum all the results
  • Divide that answer by a number that is 1 less than the total number of items
  • Take the square root of the quotient
Quartiles: Along with the Median, these are values that devide your data into 4 parts.
  • For the first quartile (Q1) find the middle number between the smallest number and the median
  • For the thrid quartile (Q3) find the middle number between the largest number and the median 
(summary of the frequency of individual values or ranges of values for a variable)

Frequency Distribution: A table showing the values in a sample and how often they occur

Inferential Statistics definition
Population: The subjects of a particular study
Parameters: A characteristic or property of a population 
Sample: A subset of the population. What data is collected
Statistic: A characteristic of a sample

Estimation of parameters
Confidence intervals: the best estimation of the parameter of a population value given the sample value.* It is equivelent to the Mean plus or minus the error of margin.
Error of margin:
  • Calculated by taking the standard deviation (or standard error)
  • Dividing it by the square root of the number of observations (> 30 if the std dev is from the sample)
  • Multiplying the result by the Confidence Interval (1.96 for a 95% confidence level and 2.576 for 99% confidence level)
Hypothesis testing
Null hypothesis: When comparing two populations, the assumption that there will be no difference between them.

Regression analysis: A statistical process for estimating relationships among variables. It is used to determine which independent variables (x) will have an impact on the main factor (dependent variable - y) you are trying to understand.

T-test: Used to determine if there is a significant difference between the means of two groups.

ANOVA: Analysis of Variance. A test for the difference between two or more means*
Library Books
HA 29 .S2365 2017 Statistics for People Who (Think They) Hate Statistics
QA 276 .W458 2013 Naked statistics
QA 276.12 .v53 2010 What is a p-value anyway?
QA 276.15 .S754 2016 The seven pillars of statistical wisdom
QA 278.2 .R33 2017 Statistics (the Easier Way)
Help Desk Statistics: unlocking the power of data

Wiley Online Ebooks

Created May 2019