Statistics for Decision Making

Bivariate Descriptive Statistics

QM 2113 -- Fall 2003

Instructor: John Seydel, Ph.D.

Student Objectives

Plot two related quantitative variables on a scatterplotEstimate the equation of the best fitting line through a set of pointsRelate the equation of a line through a set of points to the relationship between the variables being plottedUse Excel to Determine the best fitting regression line Quantify the fit of a straight line through

pointsExamine the relationship between two qualitative variables

Administrative ChoresHomework from last week Return Comments

This week’s homework Not being collected Use to study for exam Basis for discussion tonight

First exam is next week (descriptive statistics) Chapters 1-3 (selected portions, per

assignments) Chapter 11 (pages 425-429,434-446) Excel procedures as discussed in class

Review: Data and Analysis

Statistics

Quantitative Data Qualitative Data

Informal Summary Measures

Inferential Analyses

Informal Summary Measures

Inferential Analyses

The analyses can be univariate (one variable at a time), bivariate, or multivariate

Let’s Look at the Homework

Chapter 1 questions At this point, all you can do is quote

the text However, these are good final exam

questions

Chapter 3: Let’s look at #15 Any others?

How about other aspects of the assignment?

Bivariate Analyses: Quantitative Variables

Informal analysis Scatterplot Can infer relationship by looking at

points

Formal analysis Regression Involves formal means of describing

plotted line through points

Example: Great Northern Insurance

Bivariate Analyses: Qualitative Variables

Informal analysis Joint frequency tables (crosstabulation) Pie & bar charts

Formal analysis Requires understanding of basic

probability Beyond our scope for the moment

Example: KIVZ Television

Less important but need to be familiar with: Location

Median Mode Quantiles (percentiles, quartiles)

Variation Range Min and Max CV

Both (?) Z-score Empirical Rule

Other: skewLet’s look at the homework related to this

Miscellaneous Statistics

Another Notation Quiz

Mean Sample Population

Standard deviation Sample Population

VarianceRangeNumber of

Observations Elements in the population

Slope coefficientInterceptProportion of variation explained by relationshipAverage error from using regression equation for prediction

Plot two related quantitative variables on a scatterplotEstimate the equation of the best fitting line through a set of pointsRelate the equation of a line through a set of points to the relationship between the variables being plottedUse Excel to Determine the best fitting regression line Quantify the fit of a straight line through

pointsExamine the relationship between two qualitative variables

Summary of Objectives

Appendix

What is statistics all about?It’s about dealing with variation Summarizing information (description) Making decisions based upon that

summarizationType of analysis depends on data type Quantitative Qualitative

Description Formal

Numeric data: average and standard deviaiton Categorical data: percentages

Informal: frequency tables and charts data

Recall Our Purposes Here