AP Statistics Unit 3

(3.1) What cannot be inferred from observational studies?

Causation cannot be inferred from observational studies; they can only suggest associations.

(3.2) When can generalization be made?

Generalization can be made from samples that are randomly selected or otherwise representative of the population.

(3.3) What is a simple random sample (SRS)?

A simple random sample (SRS) gives every group of ‘n‘ individuals an equal chance of selection.

(3.3) What is cluster and stratified sampling respectfully?

Cluster sampling creates groups and then randomly samples entire groups. Stratified sampling creates groups and then randomly samples within each group.

(3.3) When is cluster random sampling and stratified random sampling most effective?

Cluster random sampling is effective when the sets are heterogenous and similar to one another. Stratified random sampling is most effective when strata are homogenous.

(3.4) Can observational studies determine causation?

Observational studies cannot determine causation due to possible confounding.

(3.5) What should a well-designed experiment include?

A well-designed experiment should include comparisons between at least two groups, random assignment of treatments to experimental units, replication of treatment to multiple experimental units and control of possible confounding factors.

(3.5, 3.6) What does a block design do?

Block design ensures similarity within blocks before randomization of treatments is performed and helps sperate natural variability from differences due to the blocking variable.

(3.6) What is matched pair design?

Matched pair design is a special form of randomized block design using blocks of two similar experimental units, one receiving each treatment.

Another type of matched pair design includes giving each experimental unit both treatments in a random order.

(3.7) What is statistical inference?

Statistical inference allows us to make decisions about populations or treatments of interest based on the results from sample data.

(3.7) What is considered statistically significant?

A result is considered statistically significant if the probability of observing such an extreme result by random chance is low, commonly defined as less than 0.05.