01 Foundations of Statistics and Data Collection Free Online FlashCards

What is the difference between a population and a sample?

A population is the complete group relevant to a question; a sample is the subset actually observed.

What is a census?

A census collects information from every member of the target population.

What defines probability sampling?

In probability sampling, every population unit has a known, nonzero probability of selection.

Why can convenience samples be unrepresentative?

A convenience sample uses units that are easy to reach, so participation may be related to the variables being measured.

How do categorical and quantitative variables differ?

A categorical variable assigns observations to groups or labels, whereas a quantitative variable records numerical amounts for meaningful arithmetic comparisons.

What characterizes an ordinal measurement scale?

An ordinal scale has ordered categories, but the spacing between categories is unequal or unknown.

What is operationalization?

Operationalization converts an abstract concept into a specific observable measurement rule.

How do cross-sectional and longitudinal studies differ?

A cross-sectional study measures variables at one point or short period; a longitudinal study follows units over time.

What is an observational study?

An observational study measures naturally occurring conditions without assigning the main exposure or treatment.

Why is random assignment used in experiments?

Random assignment places units into treatment groups by chance, helping balance measured and unmeasured characteristics and strengthen causal conclusions.

What is selection bias?

Selection bias occurs when recruitment or retention makes some parts of the target population more likely to be included than others.

What is a confounding variable?

A confounding variable is related to both an explanatory variable and an outcome, creating a potentially misleading association.