# STAT 1350 EXAM 1 (CSCC)

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population
all of the people of interest in a study
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sample
some of the individuals of interest
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sample survey
some of the individuals of interest are surveyed to get information about all of the individuals, aka the population
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census
an attempt to survey all of the population
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random sampling error
the error that occurs when we estimate a population characteristic by looking at only one portion of the population rather than the entire population
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confidence interval quick method
Adding and subtracting the margin of error to the sample proportion
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margin of error formula
1/square root of n, n = whole of sample
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statistic vs. parameter
Statistic: the percentage of the sample Parameter: percentage of the population
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True or False: When we take a census we try to get information from every member of a simple random sample.
False - with a census we try to get information from every member of a whole population.
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True or false: Nonsampling errors could occur, even if we take a census.
True - nonsampling errors have to do with study methods and bias, which can occur regardless of the sample.
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True or false? Margin of error only covers random sampling error.
True - margin of error does not account for nonsampling errors.
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True or false? Margin of error covers the effects of bias in the sampling method.
False - margin of error only covers random sampling errors, not bias.
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2 examples of sampling errors
Random sampling error, undercoverage
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3 examples of nonsampling errors
Nonresponse, response (wrong) error, question wording, data entry error
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How do you improve a biased sampling method?
Take a random sample of the population of interest, take a larger sample - do not use the same sampling method.
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How do we improve sampling method that yields too much variation in the resulting statistics?
Take a larger sample.
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Simple random sample vs stratified sample?
Simple random means all members of a population have an equal chance of being selected. Stratified divides the population into distinct groups (girls vs boys) and then takes random samples from there.
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Bias Reliability Validity
Bias - consistently measures +/- a number, Reliability - does not consistently measure Validity - whether it actually measures what it purports to measure
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What are the possible values of standard deviation?