AP Statistics: Sampling/Experiments

Explanatory Variable

Response Variable

• An explanatory variable is a variable whose levels are manipulated intentionally.

• A response variable is a variable that is not measured in an experiment.

• An explanatory variable is the outcome measured after treatments are administered.

• A response variable is a factor that is intentionally manipulated.

What are two poor sampling methods?

• (1) Convenience sampling and (2) voluntary response sampling.

• (1) Random sampling and (2) systematic sampling.

• (1) Stratified sampling and (2) cluster sampling.

• (1) Purposive sampling and (2) snowball sampling.

When can we make conclusions about cause and effect?

• When the researchers randomly assign the subjects to treatment groups.

• When the sample size is large enough.

• When the study is conducted in a controlled environment.

• When the results are statistically significant.

What should a well-designed experiment include?

• a. Comparisons of at least two treatment groups, one of which could be a control group.

• b. Random assignment of treatments to experimental units.

• c. Replication - enough experimental units in each treatment group to be able to detect a difference.

• d. Control of potential confounding variables, where appropriate.

What are single-blind and double-blind experiments?

• In a single-blind experiment, subjects know which treatment they are receiving, but researchers do not.

• In a double-blind experiment, only the subjects know which treatment they are receiving.

• In a single-blind experiment, subjects do not know which treatment they are receiving, but members of the research team do, or vice versa.

• In a double-blind experiment, only the researchers know which treatment a subject is receiving.

Matched Pairs Design

• A method where subjects are randomly assigned to one treatment only.

• A design where subjects are matched in pairs based on relevant factors and each pair receives both treatments.

• A design that does not involve any randomization.

• A method that only allows one treatment per subject.

How to carry out a random assignment by selecting from a hat?

• Write each subject’s name on equal-sized slips of paper and put them in a hat. Mix well and select names with replacement.

• Write each subject’s name on equal-sized slips of paper, put them in a hat, mix well, and select as many names as needed for each treatment group, without replacement.

• Write each subject’s name on different-sized slips of paper, put them in a hat, and select names randomly without mixing.

• Write each subject’s name on equal-sized slips of paper, put them in a box, mix well, and select names as needed.

Completely Randomized Design

• In a completely randomized design, treatments are assigned to experimental units completely at random.

• In a completely randomized design, treatments are assigned based on the size of the experimental units.

• In a completely randomized design, treatments are assigned in a systematic order based on time.

• In a completely randomized design, treatments are assigned only to the largest experimental units.

What is a control group?

• A group that receives the treatment of interest.

• A collection of experimental units that are not given a treatment or are given a placebo.

• A group that is used to manipulate the variables in an experiment.

• A collection of subjects that are randomly assigned to different treatments.

Stratified random sample

• A method where the population is divided into strata based on shared characteristics and a random sample is taken from each stratum.

• A sampling method where every individual has an equal chance of being selected from the entire population.

• A technique that involves selecting every nth individual from a list of the population.

• A method that only samples individuals from the largest group within the population.