1. Statistics A scientific discipline consisting of procedures for collecting, describing and interpreting numerical data

2. Statistics Statistical Procedures can be used to: 1. Summarize/describe a body of data - these procedures make up what is termed Descriptive Statistics. 2. Take information from a sample to make conclusions about a population - these procedures are called Inferential Statistics.

3. Population  A population consists of all possible observations which share an individual characteristic or set of characteristics  Identify the populations of the following studies: 1. Study of incomes of graduate students in the math department at CSULA. 2. Study of drug use among teenage boys in the US.

4. Sample  A sample is a subset of the population.  Using Inferential Statistics, information taken from the sample is used to estimate the characteristics of the population.

5. Sampling  Why sample? Why not use all the data from the population?  Normally, time and resource constraints prohibit acquiring all the data within the defined population.

6. Sampling  A sample is expected to represent the population  The way the sample is selected is a determinant of how well it represents the population  Handout of number of residents and housing units in cities in LA county Handout

7. Data  Is the data set a sample or a population?  Give an example of a study using the data in which the data would be considered:  A sample  A population

8. Biasedness  If the population of our study is all cities in California, the sampling procedure appears to be biased  A biased sampling procedure is one in which some observations in the population are favored over others in selecting the sample

9. Biasedness  If data is purposely selected only from LA County what is the chance of any city outside of the county getting within the sample?  An unbiased sampling procedure would be one in which every observation within the population has an equal chance of being selected for the sample  If the population consists of all California cities, give an example of an unbiased sampling procedure

10. Statistics  The first half of econ 209 covers Descriptive Statistics  The second half is an introduction to Inferential Statistics