TAMU STAT 201 Final Exam Study Guide
Solutions
census - ANSWER✔✔-a sample survey that attempts to include the entire population in the sample
experiment - ANSWER✔✔-a study that deliberately imposes some treatment on individuals in order to
observe their responses. The purpose is to study whether the treatment causes a change in the response
individuals - ANSWER✔✔-the objects described by a set of data. They may be people, but they may also
be animals or things
observational study - ANSWER✔✔-a study that observes individuals and measures variables of interest,
yet does not involve any intervention that will influence the responses. The purpose of such a study is to
describe some group or situation
population - ANSWER✔✔-in a statistical study, this is the entire group of individuals about which we
want information
response variable - ANSWER✔✔-a variable that measures an outcome or result of a study
sample - ANSWER✔✔-the part of the population from which we collect information and is used to draw
conclusions about the whole
sample survey - ANSWER✔✔-a type of observational study in which only a few members of a particular
group are studied. These group members are selected not because they are of special interest, but
because they represent the larger group
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variable - ANSWER✔✔-any characteristic of an individual. It can take different values for different
individuals
bias - ANSWER✔✔-(1) when the design of a statistical study systematically favors certain outcomes (2)
Consistent, repeated deviation of the sample statistic from the population parameter in the same
direction when we take many samples.
convenience sampling - ANSWER✔✔-selection of participants for a statistical study based on how easy
they are to reach. Because this method of sampling may not take an entire population into account, it is
often biased
simple random sample - ANSWER✔✔-denoted SRS, consists of n individuals from the population chosen
in such a way that every set of n individuals has an equal chance to be the sample actually selected
voluntary response sample - ANSWER✔✔-a sample that chooses itself by responding to a general
appeal, and is therefore often biased. Examples include write-in or call-in opinion polls
table of random digits - ANSWER✔✔-a table comprised of a long string of the digits 0, 1, 2, 3, 4, 5, 6, 7,
8, 9 with the following two properties: 1. Each entry in the table is equally likely to be any of the 10 digits
0 through 9. 2. The entries are independent of each other. That is, knowledge of one part of the table
gives no information about any other part
parameter - ANSWER✔✔-a number that describes a population. It is a fixed number, but in practice we
don't know the actual value of this number
statistic - ANSWER✔✔-A number that describes a sample. This is a known value when we have taken a
sample, but it can change from sample to sample. It is often used to estimate an unknown parameter.
margin of error - ANSWER✔✔-How close the sample statistic lies to the population parameter.
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level of confidence - ANSWER✔✔-Says what percentage of all possible samples satisfy the margin of
error.
confidence statement - ANSWER✔✔-A statement that says how accurate our conclusions about the
population are. The statement itself is comprised of the margin of error and the level of confidence.
variability - ANSWER✔✔-Describes how spread out the values of the sample statistic are when we take
many samples.
exit poll - ANSWER✔✔-A poll in which voters are interviewed as they are leaving the voting place.
pre-election poll - ANSWER✔✔-A sample survey that asks people how they will vote in the future.
Because people often change their minds before the election, these polls are not very reliable.
response error - ANSWER✔✔-A type of nonsampling error that occurs when a subject gives an incorrect
response. In this case, the subject's response may be a lie, the subject may remember incorrectly, or the
subject may guess at an answer without fully understanding the question.
nonsampling errors - ANSWER✔✔-Errors that are not related to the act of selecting a sample from the
population. They can be present even in a census.
processing error - ANSWER✔✔-A type of nonsampling error that involves mistakes in mechanical tasks
such as doing arithmetic or entering responses into a computer.
random sampling error - ANSWER✔✔-The deviation between the sample statistic and the population
parameter caused by chance in selecting a random sample. The margin of error in a confidence
statement includes only this type of error.
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