Chapter 1

Stats Starts Here

15 min

Statistics (the discipline) is the science of collecting, analyzing, presenting and interpreting the data. It is a way of reasoning, a collection of tools and methods, designed to help us understand the world.

Statistics (plural) are particular calculations made from data.

Data are values with a context.

What Is (Are?) Statistics?

Do those high center brake lights, required on all cars sold in U.S since 1986, really reduce rear-end collisions?

Randomized comparative experiments with fleets of rental and business cars, done before the lights were required, show that the third brake light reduced rear-end collisions by as much as 50%.

Alas, requiring the third light in all cars led to only 5% drop. Why?

Question

Descriptive Statistics refers to methods for summarizing and organizing the information in a data set.

Inferential Statistics consists of methods for estimating and drawing conclusions about population characteristics based on the information contained in a subset (sample) of that population.

Two Types of Statistics

State whether the following situations illustrate the use of descriptive or inferential statistics.

1. The average for the first test in this class is 75% with the highest score being 99%.

2. In a survey of 1000 citizens in Seattle, Washington, metropolitan area, 570 said they would pay higher prices in order to reduce greenhouse emissions. City planners conclude that 57% of all Seattle citizens would do so.

3. GCC enrollments this semester is up 14% compared to last fall.

Example

Statistics is about variation. Statistics gives us a way to work with the

variability in the world around us. Statistics helps us understand the real,

imperfect world in which we live. All measurements are imperfect, since there

is variation that we cannot see. Probability must be involved to predict

chances or errors associated with the conclusions.

Facts about Statistics

Statistics course is not really a math course! (like accounting)

Statistics can be fun! Learning to think clearly with data will open your eyes to seeing the world more clearly…

Example: ASU president Michael Crow proposed tuition increase by showing the fact that tuition cost at ASU is still in the lower one-third of senior research university tuitions.

A First Course in Statistics

ASU president Michael Crow once claimed that “Of students enrolled in the Maricopa County Community College District who are eligible to move into a state university, only 15 percent ever receive a degree.”

Example

Actual statistics: “39% of the students are attending college with a goal of transferring to a university, a decrease of about 1%, while 41% have a goal of obtaining training so they can enter the workforce, an increase of 2%. Another 16% said they were attending college for personal enrichment.”

Example