5.3 Collecting Samples

Def’ns Sampling error/variance: –Difference between the estimate derived from sample survey and “true” value that would result if census taken –The better the sample, the lower the sampling variance Response burden: –The time taken to answer surveys + time taken extracting the data

Def’ns Administrative Data: –collected as a by-product of an organisation’s day to day operations –Ex: data on births, deaths, marriages, divorces, airport arrivals, motor vehicle registrations –For example, prior to a marriage license being issued, a couple must provide the registrar with information about their age, sex, birthplace, whether previously married, and where they live.

Types of Data Collection: Census Pros –0 sampling variance –Detail about sub- groups Cons –Cost (time, money) –High response burden –Less control –Not always desirable or practical Crash-testing cars?

Types of Data Collection: Sample Survey Pros –Cost (time, money) –Lower response burden –More control Cons –Sampling variance non-zero –Not as much detail

Types of Data Collection: Administrative Data Pros –0 sampling variance –Time-series data On-going Allows trend analysis –Simplicity –Low response burden –Often free Cons –Lack of flexibility –Limited population –Definitions might change over time –Concepts and definitions not set by end-user –Data quality

How to Choose a Sampling Method? Simple random sampling Systematic random sampling Stratified random sampling Cluster/Multi-stage random sampling Destructive sampling: –Selected elements cannot be reintroduced into the population –Ex: crash-testing cars, sampling cookies

Jigsaw Day One Expert groups: –Each expert group responsible for learning one type of sampling method –Complete the handout for your method –Use your method to create a sample of 13 cards from the deck List the steps you took List the cards Use the random # generator on your calculator to create random #

Jigsaw Day Two Home groups –Each group has one “expert” in a different sampling method –Teach the other members of your home group about your method (5 minutes each) –Use the cards to demonstrate your method –Work on handout

Description Advantages Disadvantages Examples Non-text example Card Sample