In this lecture I’ll go over the vocabulary from the text and present some examples.
Study: In Breeding in blue whales.
New York Times, 1/23/2024 photo cred: Burton Lim
n = 3500
Four subspecies1:
Northern
Northern Indian Ocean
Pygmy blue whale
Antarctic subspecies
The population is all the Blue Whales left in the world
The sample is the 35 Blue Whales that have washed ashore.
Simple random sampling
Stratified sampling
Convenience sample
Control vs Treatment
Randomization - Effect of Confounding Variables.
Replication - Repeat experiments have the similar results.
Experiments have a control
Observational Studies often gather information
If we suspect a causal relationship we have an explanatory (independent) and response variable (dependent).
Negative relationship
Positive Relationship
No Relationship
Variables that have an unanticipated effect on the study.
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
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.
Chapter 4 Exploring Categorical Data