Z519: Information Analytics

Social Statistics: Introduction

Statistics describes a set of tools and techniques for describing, organizing and interpreting information or data.

Do we need statistics? When and Why?

Social Statistics

Everybody relies on data in one way or another: corporate presidents decide company policy

based on quarterly sales figures politicians decide on campaign strategy based

on polls teachers decide grading curves based on a bell

curve you and I decide whether to smoke or not

based on health records of other people Therefore, we need a comprehensive and

understandable way to deal with data: Statistics is the study of making sense of

data.

Why we need statistics

Asking the research question Formulating the hypotheses Collecting data Analyzing data Evaluating the hypotheses

The research process

Questions What factors affect the economic mobility of female

workers Do male and female use twitter differently?

Hypothesis A relationship between two variables Variable is a property which can take two or more values Unit of analysis: individual, group, organization, nation Dependent variable: the variable the researcher wants

to explain (the “effect”) Independent variable: the variable that “cause” or

account for the dependent variable Gender cause wage difference (gender: is independent variable,

wage difference is dependent variable)

The research process

What are independent and dependent variables Younger Americans are more likely to support

stricter gun control laws than older Americans People who attend church regularly are more

likely to oppose abortion than people wo do not attend church regularly

Elderly women are more likely to live alone than elderly men

Individuals with postgraduate education are likely to have fewer children than those with less education.

Independent vs. dependent variables

Cause-and-effect relationship The cause has to precede the effect in

time There has to be an empirical relationship

between the cause and the effect This relationship cannot be explained by

other factors.

Causation

Used to organize and describe the characteristics of a collection of data

Descriptive statistics

How can you describe this table?

Descriptive statistics

Name Gender

Major Age Score

Sara Female LIS 27 A

Richard Male Psychology 30 C

Andrea Male Education 33 B

Emily Female Language 25 B

Bill Male LIS 28 C

Leo Female Psychology 26 A

Liz Female LIS 26 B

Alice Female LIS 28 C

Steven Male Psychology 24 C

Jeff Male LIS 30 B

Make inferences from a smaller group of data to a possible larger one Sample: a smaller group of data Population: the whole group of a certain

subject

Inferential statistics

population the set of all photographs of Mars the set of heights of people in the US Army the set of all measurements of water quality taking from

the Lake Monroe the set of all problems that can be solved using statistics.

sample the pictures selected from a specific region of Mars the heights of people in a particular division of the US

Army the set of water measurements of the Lake Monroe taken

on 1/12/2015 the statistical problems we are solving in this class

Population & Sample

Problem definition what is the population of interest, and what are the variables that are to be investigated

Data collection describe and select the sample from the population

Data analysis make some statistical inferences from the sample about the population

Analysis Reporting report the inference together with a measure of reliability for the inference where we use the term variable to mean a characteristic or property of an individual population where the observations can vary.

Steps for statistical analysis

Example: A tax auditor is responsible for 25,000 accounts. How many accounts are in error?

Defining the problem: The entire population consists of all 25,000 accounts. Our goal is to obtain a reasonable estimate for the number of accounts that are, in all likelihood, in error. Our variable x counts whether an account is in error.

Data collection and summary: The auditor decides to select 2000 accounts at random, tests each of these, and finds that 84 of them are in error.

Data analysis: In this case, the likely theory involves computing 84/2000 = 4.2%.

Analysis reporting: Based on our data analysis we infer that approximately 4.2% of the accounts will be in error.

An example

Excel Excel Toolpak SPSS/PASW

Tools

1. Click the green File tab, and then click on Options.2. Click Add-Ins, and then in the Manage box, select

Excel Add-ins.3. Click Go.4. In the Add-Ins available box, select the Analysis

ToolPak check box, and then click OK. 5. If you get prompted that the Analysis ToolPak is not

currently installed on your computer, click Yes to install it.

6. After you load the Analysis ToolPak, the Data Analysis command is available in the Analysis group on the Data tab.

Excel Toolpak (1)

Powerful, reliable, accessible, easy, and free

Excel Toolpak (2)

Operator Symbol Example What it does

Addition + =2+5 Adds 2 and 5

Subtraction - =5-3 Subtracts 3 from 5

Division / =10/5 Divides 10 by 5

Multiplication * =2*5 Multiplies 2 times 5

Power of ^ =4^2 4 power of 2

Formula

How does it work in Excel?

So let's get started digging into what makes a spreadsheet work. Spreadsheets are made up of: columns Rows cells

In each cell there may be the following types of data: text (labels) number data (constants) formulas (mathematical equations)

Basics of a Spreadsheet

Column

Row

Cell

data types examples descriptions

LABEL Name or Wage or Days

anything that is just text

CONSTANT 5 or 3.75 or -7.4 any number

FORMULA =5+3 or = 8*5+3 math equation

Types of Data

ALL formulas MUST begin with an equal sign (=).

The Sum function takes all of the values in each of the specified cells and totals their values. The syntax is: =SUM(first value, second value, etc)

Formulas – SUM

The average function finds the average of the specified data. The syntax is as follows =Average(first value, second value, etc.)

Formulas – AVERAGE

MAX: This will return the largest (max) value in the selected range of cells.

MIN: This will return the smallest (Min) value in the selected range of cells.

Formulas – MAX/MIN

This will return the number of entries (actually counts each cell that contains number data) in the selected range of cells.

Formulas – COUNT