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Math Chapter 4 Vocab
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Gravity
Terms in this set (44)
population
the entire group of individuals about which we want information
sample
part of the population from which we actually collect information. Use info to draw conclusions about the entire population
sample survey
studies that use an organized plan to choose a sample that represents some specific population;
selects a sample from the population of all individuals about which we desire information
convenience sample
choosing individuals who are easiest to reach
bias
using a method that will consistently overestimate or underestimate the value you want to know; a study that systematically favors certain outcomes
voluntary response samples
people who choose themselves by responding to a general appeal, show bias because people with strong opinions are most likely to respond
random sampling
the use of chance to select a sample
simple random sampling
n individuals from the population chosen in such a way that ever set of n individuals has an equal chance to be the sample actually selected; gives every possible sample of a given size the same chance to be chosen
table of random digits
a long string of digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
each entry is equally likely to be any of the 10 digits 0 through 9
the entries are independent of each other
stratified random sample
classify the population into groups of similar individuals, called strata
choose a separate SRS in each stratum and combine these SRSs to form the full sample
cluster sample
divide population into smaller groups that, ideally, 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
cluster
...
inference
the process of drawing conclusions about a population on the basis of sample data
margin of error
...
sampling frame
list of individuals from which we will draw our sample
undercoverage
some groups in the population are left out of the process of choosing the sample
nonresponse
an individual chosen for the sample can't be contacted or refuses to participate
response bias
systematic pattern of incorrect responses in a sample survey
wording of questions
can influence responses
sampling errors
mistakes made in the process of taking a sample that could lead to inaccurate information about the population
non sampling errors
errors that can plague even a census
observational study
observes individuals and measures variables of interest but does not attempt to influence the responses
experiment
deliberately imposes some treatment on individuals to measure their responses
lurking variable
variable that is not among the explanatory or response variables win a study but that may influence the response variable
confounding
two variables are associated in such a way that their effects on a response variable cannot be distinguished from each other
treatment
specific condition applied to the individuals in an experiment
experimental units
smallest collection of individuals to which treatments are applied
subjects
human beings that are the experimental units
factors////
explanatory variables
level////
specific value
random assignment
experimental units are assigned to treatments at random, that is, using some sort of chance process; this helps create roughly equivalent groups of experimental units by balancing the effects of lurking variables that aren't controlled on the treatment groups
completely randomized design
treatments are assigned to all the experimental units completely by chance
control group////
purpose: to provide a baseline for comparing the effects of the other treatments
control///
for lurking variables that might affect the response; use a comparative design and ensure that the only systematic difference between the groups is the treatment administered
replication
use enough experimental units in each group so that any differences in the effects of the treatments can be distinguished from chance differences between the groups
placebo ///
fake treatment, given to a control group
placebo effect
response to a dummy treatment
double-blind
neither the subjects nor those who interact with them and measure the response variable know which treatment a subject received
single- blind
subjects are unaware of which treatment they are receiving, but the people interacting with them and measuring the response variable do know OR subjects know which treatment they are receiving but people interacting with them and measuring the response variable don't
statistically significant
an observed effect so large that it would rarely occur by chance
block
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
randomized blocking design
random assignment of experimental units to treatments is carried out separately within each block
matched pairs design///
common type of randomized block design for comparing two treatments; to create matching pairs of similar experimental units; the random assignment of subjects to treatments is done within each matched pair
Lack of realism
When the subject or treatments or setting of an experiment don't realistically duplicate conditions we want to study
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