AP Statistics Chapter 4 Flashcards

Sampling and Surveys

6738273724	Bias	The design of a statistical study shows bias if it systematically favors certain outcomes.	0
6738273725	Census	A study that attempts to collect data from every individual in the population.	1
6738273726	Cluster sample	To take a cluster sample, first divide the population into smaller groups. Ideally, these clusters should mirror the characteristics of the population. Then choose an SRS of the clusters. All individuals in the chosen clusters are included in the sample.	2
6738273727	Convenience sample	A sample selected by taking the members of the population that are easiest to reach; particularly prone to large bias.	3
6738273728	Double-blind	An experiment in which neither the subjects nor those who interact with them and measure the response variable know which treatment a subject received.	4
6738273729	Margin of error	A numerical estimate of how far the sample result is likely to be from the truth about the population due to sampling variability.	5
6738273730	Nonresponse	Occurs when a selected individual cannot be contacted or refuses to cooperate; an example of a nonsampling error.	6
6738273731	Nonsampling error	The most serious errors in most careful surveys are nonsampling errors. These have nothing to do with choosing a sample—they are present even in a census. Some common examples of nonsampling errors are nonresponse (people don't answer), response bias (people lie), and errors due to question wording.	7
6738273732	Population	In a statistical study, the entire group of individuals about which we want information.	8
6738273733	Random sampling	The use of chance to select a sample; is the central principle of statistical sampling; allows us to infer results to the population	9
6738273734	Response bias	A systemic pattern of incorrect responses; "people lie"	10
6738273735	Sample	The part of the population from which we actually collect information. We use information from this to draw conclusions about the entire population.	11
6738273736	Sampling error	Mistakes made in the process of taking a sample that could lead to inaccurate information about the population. EX. bad sampling methods (convenience and voluntary response) and undercoverage	12
6738273739	Simple random sample (SRS)	Gives every possible sample of a given size the same chance to be chosen. We often choose this type of sample by labeling the members of the population and using random digits to select the sample.	13
6738273740	Strata	Groups of individuals in a population that are similar in some way that might affect their responses.	14
6738273741	Stratified random sample	First classify the population into groups of similar individuals (mini populations). Then choose a separate SRS from each stratum to form the full sample.	15
6738273742	Table of random digits	A long string of the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 with these properties: • Each entry in the table is equally likely to be any of the 10 digits 0 through 9. • The entries are independent of each other. That is, knowledge of one part of the table gives no information about any other part.	16
6738273743	Undercoverage	Occurs when some members of the population are left out of the sampling frame; a type of sampling error.	17
6738273744	Voluntary response samples	People decide whether to join a sample based on an open invitation; particularly prone to large bias.	18
6738273745	Wording of questions	The most important influence on the answers given to a survey. Confusing or leading questions can introduce strong bias, and changes in wording can greatly change a survey's outcome. Even the order in which questions are asked matters.	19
6738273746	Block	A group of experimental units that are known before the experiment to be similar in some way that is expected to affect the response to the treatments.	20
6738273747	Completely randomized design	When the treatments are assigned to all the experimental units completely by chance.	21
6738273748	Confounding	When two variables are associated in such a way that their effects on a response variable cannot be distinguished from each other.	22
6738273750	Control group	An experimental group whose primary purpose is to provide a baseline for comparing the effects of the other treatments. Depending on the purpose of the experiment, this group may be given a placebo or an active treatment	23
6738273751	Double-blind	An experiment in which neither the subjects nor those who interact with them and measure the response variable know which treatment a subject received.	24
6738273752	Experiment	Deliberately imposes some treatment on individuals to measure their responses.	25
6738273754	Explanatory variable	A variable that helps explain or influences changes in a response variable.	26
6738273755	Factor	The explanatory variables in an experiment are often known as these	27
6738273757	Lurking variable	A variable that is not among the explanatory or response variables in a study but that may influence the response variable.	28
6738273758	Matched pair	A common form of blocking for comparing just two treatments. Often each subject receives both treatments in a random order. In others, each subject is matched to another subject who is very similar and results are compared.	29
6738273759	Observational study	Observes individuals and measures variables of interest but does not attempt to influence the responses.	30
6738273760	Placebo	An inactive (fake) treatment.	31
6738273761	Placebo effect	Describes the fact that some subjects respond favorably to any treatment, even an inactive one (placebo).	32
6738273762	Random assignment	Use some chance process to assign experimental units to treatments. This helps create roughly equivalent groups of experimental units by balancing the effects of lurking variables that aren't controlled on the treatment groups. Allows us to infer cause and effect.	33
6738273763	Randomized block design	Start by forming blocks consisting of individuals that are similar in some way that is important to the response. Random assignment of treatments is then carried out separately within each block.	34
6738273765	Response variable	A variable that measures an outcome of a study.	35
6738273768	Subjects	Experimental units that are human beings.	36
6738273769	Treatment	A specific condition applied to the individuals in an experiment. If an experiment has several explanatory variables, a treatment is a combination of specific values of these variables.	37
6738273771	Inference about cause and effect	Requires a well-designed experiment in which the treatments are randomly assigned to the experimental units.	38
6738273772	Inference about the population	Using information from a sample to draw conclusions about the larger population. Requires that the individuals taking part in a study be randomly selected from the population of interest.	39