1. 1. Introduction

2. What is statistics? Statistics as a subject provides a body of principles and methodology for : - (1) designing the process of data collection, - (2) summarizing and interpreting the data, - (3) and drawing conclusions or generalities.

3. Three branches of Statistics (1) designing the process of data collection = Experimental Design. (2) summarizing and interpreting the data = Descriptive Statistics. (3) and drawing conclusions or generalities = Inferential Statistics.

4. Population vs. Sample A (statistical) population includes each element from the set of observations that can be made. A sample consists only of observations drawn from the population.

5. Population vs. Sample The population for a study of how long an infant might be all children born in the UK in the 1980's. The sample might be lengths of all babies born on 7th May in any of the years.

6. Population vs. Sample We want to know things about populations. But we do not have the data of population. Because: Collecting the population data often impractical or impossible. Instead, we collect a sample data. Example: If a company's customer service division wanted to learn whether its customers were satisfied, it would not be practical (or perhaps even possible) to contact every individual who purchased a product. Instead, the company might select a sample of the population.

7. Population vs. Sample Example: You want to know the mean income of the subscribers to a particular magazine—a parameter of a population. You draw a random sample of 100 subscribers. The sample mean income is $27,500 (a statistic). You conclude that the population mean income is likely to be close to $27,500 as well.

8. Sample Size The number of observations in a sample is its sample size. Usually, a sample has sample size less than or equal 30 is a small sample, otherwise it is a large sample.

9. Group work - Collecting a sample 1) Determine the number of hours per day OU student plan to study. 2) Determine the number of hours per day this year freshman in OU plan to study. - Collect a large sample from the population. -Describe how you collect your sample data. -Present your sample data. -Write some comments, or draw some conclusion, hypothesis about the data. - Work in group of 2 and turn in a typed-in solution. - Due: August, 31 st.