1 1 Overview of Statistics Data consist of

1. 1 Overview of Statistics Data: consist of information coming from observations, counts, measures, or responses. The singular for data is datum. Statistics: is the science of collecting. Organizing, analyzing, and interpreting data in order to make decisions.

Population vs. Sample • A population is the collection of all outcomes, responses, measurements, or counts that are of interest. • Examples are: – All adults – All trees – All students, etc

Population vs. Sample • A sample is a subset of population. • Examples are: – All adults that took the survey – All trees that were looked at – All the students the interviewer talked to

Population vs. Sample • What are some benefits of samples? – May be impossible to get the entire population – Samples are less expensive in time, resources, and money • What are some problems with samples? – Sample may not represent the population. – What are some difficulties of getting a sample?

Examples from the book • Try it Yourself – pg 3 – Population consists of the prices per gallon of regular gasoline at all gasoline stations in the U. S. – The sample consists of the prices per gallon of regular gasoline at the 800 surveyed stations – The data set consists of the 800 prices.

Parameter vs. Statistic • A parameter is a numerical description of a population characteristic. • Examples: – The true “average” height of adult human males in the US. – The number of individuals in Mexico that have paid a bribe to a police officer. – The actual median income in Conyers.

Parameter vs. Statistic • A statistic is a numerical description of a sample characteristic. • Examples: – The “average” height of a random sample of 1, 000 adult human males in the US. – The percentage of individuals in a random sample of 10, 000 adults in Mexico that have paid a bribe to a police officer, multiplied by the size of the adult population in Mexico. – The median income of a random sample of 1, 000 adults in Conyers.

• Study Tip: The terms parameter and statistic are easy to remember if you use the mnemonic device of matching the first letters on population parameter and the first letters of sample statistic.

Examples from the book • Try it Yourself – pg 4 – Population – Parameter – What could have been a sample? – Would the number for the sample been a parameter or a statistic? – Statistic

Descriptive vs. Inferential Statistics • Descriptive statistics is the branch of statistics that involves the organization, summarization and display of data. This is what we have been doing. We only talked about the data we were studying, with no “therefore this happens to the world. ”

Descriptive vs. Inferential Statistics • Inferential statistics is the branch of statistics that involves using a sample to draw conclusions about a population. A basic tool in the study of inferential statistics is probability. You are making a larger conclusion than what you studied.

Examples from the book • Try it Yourself – pg 5 – Descriptive statistics involve the statement “ 76% of women and 60% of men had a physical examination the previous year. ” – An inference drawn from the study is that a higher percentage of women had a physical examination within the previous year.

Homework • HW: pg 6, # 1 – 25 all