Lesson 7: Sampling and Inference
September 17, 2024
Review:
- Exam 1 Results
- Median = 92.5
- Mean = 90.9
- Standard Deviation = 8.9
- Exam 1 Solutions
- Court of Appeals
Presentation:
- Census and Sampling
- Census = attempt to count entire population
- US Census every 10 years
- Most costly non-military federal government operation (except bailing out Wall Street)
- Sample = gather info from a portion of the population
- Sample Types
- Voluntary response sample
- Complete an optional survey
- Inherent bias
- Example: Survey Monkey
- Simple random sample
- select from a population
- each individual has equal chance of being selected
- Example: random selection of subset of enrolled students
- Stratified random sample
- divide population into groups or strata
- random sampling, equal chance of selection within each group
- Example: random selection within major (30% CIS, 35% Mgmt, 35% Econ)
- Voluntary response sample
- Sample Types
- Video: Census and Sampling
- Census = attempt to count entire population
- Samples and Surveys
- Toward Statistical Inference
- Population parameters
- Sample statistics
- Sampling distribution
- Bias and Variability
- to reduce bias, use random sampling
- to reduce variability, use larger sample sizes (p. 215)
- Margin of Error Calculator
- Video: Samples and Surveys
- Toward Statistical Inference
Activity:
- Choose a “battleground” State: AZ, GA, MI, NV, NC, PA, VA or WI
- Select a recent corresponding poll on The Hill (or similar)
- Identify the sample size
- Estimate the population size (registered voters)
- Calculate margin of error using 95% confidence
Assignment:
- Read about how to calculate margin of error (Survey Monkey)
- Read the September 16 issue of The Tilt (NY Times)