Post on 06-Jan-2016
description
Chapter 1 Getting Started
What is Statistics?
Individuals vs. Variables
Individuals• People or objects included
in the study
Variables• Characteristic of the
individual to be measured or observed
Quantitative vs. Qualitative
Quantitative Variables• Have value or numerical
measurement for which operations such as addition or averaging make sense
Qualitative Variables• Describes an individual by
placing the individual into a category or group, such as male or female
Population vs. Sample
Population Data• Data is from every
individual of interest• Population Parameters are
numerical measures that describe an aspect of a population
Sample Data• The data are from only
some of the individuals of interest
• Sample Statistics are numerical measures that describe an aspect of a sample
Levels of Measurement
• Nominal – Names, Labels, Categories• Ordinal – Arranged in meaningful
mathematical order• Interval – Differences are meaningful• Ratio – Division or percentage comparisons
make sense; zero point
Chapter 1 Getting Started
1.2 Random Samples
Simple Random Sample (SRS)
• A simple random sample of no measurements from a population is a subset of the population selected in such a manner that every sample of size n from the population has an equal chance of being selected.
Random Number Tables (RNT)
• Used to help secure a SRS• Steps:– Number all members of the population
sequentially.– Drop a pin on the RNT to pick a starting point– Pull digits n at a time, discarding non-used
numbers– Repetition?
Other Methods to Secure a SRS
• Systematic• Stratified• Cluster• Multistage• Convenience
Systematic Sampling
• Population is numbered• Select a starting point at random and pick
every kth member
Stratified Sampling
• Divide population into distinct subgroups based on specific characteristics
• Draw random samples from each strata
Cluster Sampling
• Divide population into pre-existing segments or clusters (often geographic).
• Make a random selection of clusters.• All members of cluster are chosen.
Multistage Sampling
• Use a variety of sampling methods to create successively smaller groups at each stage.
• Final sample is made of clusters.
Convenience Sampling
• Create sample by selecting population members which are easily available