AP Statistics - Chapter 4 Review

It is random

Personal choice. Convenience Survey and Voluntary Surveys

Undercoverage: When certain members of the population are unaccounted for or are less likely to be included in the sample.

Nonresponse: When an individual is picked as part of a sample but chooses not to be included.

Response Bias: Pattern of inaccurate responses due to the wording of a question.

Sample: Includes people/things you select from the population.

Sampling: Method of selecting samples.

A good sampling method where every group is equally likely to be chosen. USE HAT METHOD

Entire group of individuals we want information about.

Sampling individuals that are easy to reach. BAD SAMPLE BECAUSE THEY INVOLVE PERSONAL CHOICE

People choose to be in the sample. BAD SAMPLING METHOD

Group of experimental units that are known to be similar.

Separate subjects into blocks then randomly assign to treatments within each block.

Experiment to compare two treatments that uses blocks of size 2. Very similar experimental units are pairs then randomly assigned to a treatment. OR giving each subject the same treatment in a different order.

EX: Two highest students are grouped together and each one is separated into different treatments.

Each subject received both treatments but in a different order.

Block is meant for experiments
Stratified is sampling, how we pick people.

Number that describes some characteristic of a population.

Sampling method that involves using chance to determine which member of a population are included.

Collects data from every individual in the population.

Number that describes characteristics of a sample.

If something is very likely to under or overestimate a value in a statistical study.

A study that observes individuals and measures variables of interest but does not influence the responses.

When two variables are similar in a way that their effects on a response cannot be distinguished from one another.

EX: Two very smart people

A specific condition applied to the individuals in an experiment.

Group used to serve as a baseline for comparison. Treatment group that gets no treatment.

Measures an outcome of a study.

Where a treatment is randomly assigned to an experiment. Humans are called subjects.

EX: Waxed boxes and plastic boxes are experimental units that will be tested under different temperatures

Some subjects will respond favorably to any treatment.

A treatment has no active ingredient but is like other treatments.

An explanatory variable that is manipulated and may cause a change in the response variable.

If neither the subjects or those who interact with them know which treatment a subject is getting.

Label all the people in the population, look at the table and select the amount of people being sampled (EX: 10 people from a population of 100). From there, say that a random number from 001-100 will be chosen 10 times.

Take a simple random sample from the population.

Splits population into groups (strata’s) and chooses an SRS from each group. Strata is based on some variable that is known or suspected to alter the results.

Splits population intro groups based on location (clusters). Sample includes every individual in each selected cluster. They are used for efficiency.

Selects members from a larger population from a list. A random starting point is chosen and then you select every n’th member for your study.

Overall effort to minimize variability and confounding between variables.

When the observed differences in the results of an experiment are so large that it is unlikely they occurred by chance.

random selection

random assignment

Random Assignment W/ groups
Yes no
Yes Inference to Inference to population=yes

cause and effect cause and effect = no
yes

No Inference to
population=no

cause and effect cause and effect = no
yes

Comparison to a control, replication, randomization.

When individuals were randomly assigned to groups.

This experiment is NOT statistically significant because the probability of _______ exceeds the 5% threshold. Therefore, this is likely to occur by chance.

This experiment is statistically significant because the probability of ____ is less than the 5% threshold. Therefore, these results are unlikely to occur by chance alone.

When you have random selection.

ONLY if it is an experiment, NOT an observational study.

overestimate/underestimate

Using a representative sample from the target population can cause inferences to be make which can be relayed back to the population.

without replacement

The results were no better than what could be expected by chance through random assignment of the treatments.

Usually, a random block design takes into account hidden variables.

When you separate subjects into groups and then assign the treatment there to reduce confounding.