1.3 – Introduction to Experimental Design

Vocabulary• Census

• Sample

• Simulation

Basic guidelines for planning a statistical study:

1. First, identify the individuals or objects of interest.2. Specify the variables as well as protocols for taking measurements or

making observations.3. Determine if you will use an entire population or a representative

sample. If using a sample, decide on a viable sampling method.4. In your data collection plan, address issues of ethics, subject

confidentiality, and privacy. If you are collecting data at a business, store, college, or other institution, be sure to be courteous and to obtain permission as necessary.

5. Collect the data.6. Use appropriate descriptive statistics methods/ inferential statistics

methods.7. Finally, note any concerns you might have about your data collection

methods and list any recommendations for future studies.

Experiment vs Observation

• Observational Study:

• Experiment:

Experiments and Observation

• Placebo Effect:

• Control Group:

• Lurking/Confounding Variables:

• Replication:

• Bias:

Experiments

• Randomized Two-Treatment Experiment:

• Double Blinded Experiment:

Guided Exercise #5

• With table partners, turn to page 22– Cover answers– Discuss answers• Check

– Whole group clarification

Surveys

• Survey

Keep in mind:• Are questions asked in a neutral way?• Are biases built into wording?• Is the interviewer giving subtle feedback that influences

the response?• How can you make sure the respondents are being

truthful?• Is the sample representative of the population?

Surveys

• Likert Scale:• Pitfalls:– Nonresponse:– Voluntary Response:– Hidden Bias:– Other Variables– Generalizing Results:

Guided Exercise #6

• With table partners, turn to page 24– Cover answers– Discuss answers• Check

– Whole group clarification

Checkpoint

Explain the importance of random samples

Construct a simple random sample using random numbers

Simulate a random process

Describe stratified, cluster, systematic, and convenience sampling.

Homework

• Read Pages 19-24– Take notes on what we have not covered

• Do Problems – Page 25 (1-4)

• Not multiple choice!• Check odds in back of book

• Read and preload Review information– Page 26-29

• Know vocabulary• Try Chapter Review Problems (not graded, but helpful)