Intro to Study Vocabulary

Schwab

Read before hand

Chapter 2 on Study Design

Overview

In this lecture I’ll go over the vocabulary from the text and present some examples.

Blue whales

Study: In Breeding in blue whales.

New York Times, 1/23/2024 photo cred: Burton Lim

Some info on Blue whales:

n = 3500

Four subspecies1:

  • Northern

  • Northern Indian Ocean

  • Pygmy blue whale

  • Antarctic subspecies

Population vs Sample

The population is all the Blue Whales left in the world

The sample is the 35 Blue Whales that have washed ashore.

Sampling Strategies

  1. Simple random sampling

  2. Stratified sampling

  3. Convenience sample

Experimental Design

  1. Control vs Treatment

  2. Randomization - Effect of Confounding Variables.

  3. Replication - Repeat experiments have the similar results.

Experiments vs Observational Studies

  1. Experiments have a control

    1. Use for causal conclusions
  2. Observational Studies often gather information

    1. Cannot be used for casual conclusions

Explanatory and Response

If we suspect a causal relationship we have an explanatory (independent) and response variable (dependent).

  • Negative relationship

  • Positive Relationship

  • No Relationship

Confounder Variables

Variables that have an unanticipated effect on the study.

You try

Chapter 2 2.12 and 2.20

Solution 2.12

a. Observational Study. There is no control group.

b. No we cannot see for sure if there is a link between stress and muscle cramps.

c. It could be that (perhaps) there is a link between excess coffee and lack of sleep that causes cramps

Solution 2.20

a. This was an experiment there is a control group (placebo).

b. Explanatory is the quantity of vitamin C. The response is cold duration

c. The patients were blind during their treatment, all pills look the same

d. The study is not double blind as the nurses knew which patient got which pill

e. A Confounding variable is whether a patient takes the pill.

Next Reading

Chapter 4 Exploring Categorical Data