Chapter 4 Flashcards
population
entire group of individuals we want information from
census
collects data from every individual in the population
sample
subset of individuals in the population we collect data from
sample survey
a study that collects data from a sample to learn about the population from which the sample was selected
convince sampling
selects individuals from the population who are easy to reach
bias
the design of a statistical study shows bias if it is likely to underestimate or overestimate the value you want to know
voluntary response sampling
allows people to choose to be in the sample bu responding to a general invitation
random sampling
involves using a chance process to determine which members of a population are included in the sample
simple random sampling (SRS)
chosen in a way that every group of n individuals in the population has an equal chance to be selected as the sample
sampling with replacement
an individual from a population can be chosen more than once; they are put back into the sample
sampling without replacement
an individual from a population can only be chosen once; once they are sampled they are put to the side
strata
groups of individuals in a population who share characteristics though to be associated with the variables being measured in a study
stratified random sampling
selects a sample by choosing an SRS from each stratum and combining the SRSs into one overall sample
some from all
cluster
a group of individuals in the population that are located near each other
cluster sampling
selects a sample by randomly choosing clusters and including each member of the selected clusters in the sample
all from some
systematic random sampling
selects a sample from an ordered arrangement of the population by randomly selecting one of the first k individuals and choosing every 5th individual after
under coverage
occurs when some members of the population are less likely to be chosen or can’t be chosen in a sample
nonresponse
occurs when an individual chosen for the sample can’t be contacted or refuses to participate
response bias
occurs when there is a systematic pattern of inaccurate answers to a survey question
observational study
observes individuals and measures variables of interest but does not attempt to influence the responses
just watching
confounding
occurs when two variables are associated in such a way that their effects on a response variable can not be distinguished from each other
experiment
deliberately imposes treatments/conditions onto individuals to measure their responses
placebo
a treatment that has no active ingredient but is otherwise like the other treatments
the control group
treatment
a specific condition applied to the individuals in an experiment
experimental unit
an object to which a treatment is randomly assigned
subjects
when the experimental units are humans
factor
levels
an explanatory variable that is manipulated and may cause a change in the response variable
different values of a factor
control group
used to provide a baseline to compare the effects of the other treatments
placebo effect
the fact that some subjects in an experiment will respond favorably to any treatment, even if its inactive
gaslighting yourself into thinking its working
double blind
single blind
total cluelessness, neither the subjects nor those imposing the treatment know what treatment the subject is receiving; helps eliminate bias
partial cluelessness, either the subject or those imposing the treatment know what treatment the subject is receiving
control
keeping other variables constant for all experimental units
replication
giving each treatment to enough experimental units so that a difference in the effects of treatments can be distinguished from chance variation due to random assignment
completely randomized design
the experimental units are assigned to treatments completely at random
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 treatments
randomized block design
the random assignment of experimental units to treatments is carried out separately within each block
matched pairs
compares two treatments that uses block sizes of 2
can be two similar experimental units paired with each other and the treatments are randomly assigned to each person in the pair
each experimental unit can be matched with themselves and the experimental unit would receive both treatments and whatever treatment to start would be randomly selected
sampling variability
the fact that different random samples of the same size from the same population produce different estimates
statistically significant
observed results of a study are too unusual to be explained by chance
5% threshold: this would be below 5%
multistage sampling
two or more sampling methods combined
