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

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.

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

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.

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.

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

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

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

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

Statistics The first half of econ 3060 covers Descriptive Statistics The second half is an introduction to Inferential Statistics