36 terms

lhsmrpTEACHER

voluntary response sample

sampling design where individuals can choose on their own whether to participate in the sample; DANGER - will usually produce biased result

undercoverage

occurs when some groups in the population are left out of the process of choosing the sample; DANGER - will usually produce biased result

nonresponse

occurs when an individual chosen for the sample can't be contacted or refuses to participate; DANGER - will usually produce biased result

response bias

a systematic pattern of incorrect responses

sampling frame

a list of individuals from whom the sample is drawn; preferably, the entire population

sample

items selected from a population, and examined in order to gather information/data

population

the ENTIRe group of individuals we want information about

matched pairs design

common form of blocking for comparing just two treatments by matching pairs of similar experimental units

block design

the random assignment of units to treatments carried out separately within groups of experimental units that are expected BEFORE the experiment to systematically affect the response to the treatments (contrasted with completely randomized design)

double-blind experiment

neither the subject nor those who measure the response variable know which treatment an experimental unit received

hidden bias

unobserved variables that may cause bias in the measurement of the response variable

replication

using enough experimental units to reduce chance variation

statistically significant

an observed effect so large that it woud rarely occur by chance; this does not mean that the effect is large enough to be important

completely randomized experiment

when all experimental units are allocated at random among all treatments (as contrasted with a block design)

randomization (in an experiment)

relying on chance to make assignments to treatment groups; the assigment does NOT depend on any characteristic of the experimental unit and does NOT rely on the judgment of the experimenter in any way

control group

the group that receives no treatment (or a sham treatment)

systematic random sample

a type of probability sampling method in which sample members from a larger population are selected according to a random starting point and a fixed periodic interval

observational study

we observe individuals and measure variables of interest but do not attempt to influence the responses

experimental units

the individuals on which the experiment is done

subjects

when the experimental units are humans (or anthropomorphized)

factor

the explanatory variable (there may be several) in an experiment

level

the specific treatment value (there may be several) of an experiment's factor

placebo effect

a favorable response to a dummy treatment — an experimental result caused by expectation alone

strata

groups of individuals that are similar in some way that is important to the response

stratified random sample

after dividing the population into STRATA, a separate simple random sample (SRS) occurs in each stratum and them combined into the full sample

probability sample

a sample chosen by chance; after knowing what samples are possible and what chance (probability) each possible sample has

table of random digits

a long string of digits 0-9 with two properties: (1) each entry is equally likely to be any of the ten digits, and (2) the entries are independent of each other (the knowledge of one part of the table gives no information about any other part)

simple random sample

individuals chosen from a population in such a way that every SET of that size has an equal chance to be the sample actually selected

SRS

simple random sample

biased

any method or practice that systematically favors certain outcomes

convenience sampling

choosing individuals who are easiest to reach

randomization (in a survey)

relying on chance to select a sample from the population; the selection does NOT depend on any characteristic of the individuals and does NOT rely on the judgment of the selector in any way

control

the overall effort to minimize variability in the way that experimental units are obtained and treated

sampling

involves studying a part in order to gain information about the whole

census

an attempt to contact every individual in a population in order to gain information

cluster sampling

after dividing the population into groups or clusters, some of these are randomly selected; then ALL individuals in the chosen clusters are selected to be in the sample