Lec 1 Intro Flashcards
sample of convenience
collection of individuals that just happen to be available at the time
Statistics
the study of methods to describe and measure aspects of nature from samples. Provides tools to quantify the uncertainty of these measures allowing us to determine their likely magnitude of departure from the truth
Variable
characteristic measured on individuals drawn from a population under study
Data
measurements of one or more variables made on a collection of individuals
Explanatory vs response variable
try to predict or explain a response variable from an explanatory variable
explanatory doesn’t necessarily determine response variable, however can help predict it
SUBJECTIVE
parameter
a property of the population/describes some aspect of that population, ex mean height
population
group of all individuals that we care about
sample
individuals from population we have access to/measurements from
relationship estimates sample parameters population
estimates from the sample of the parameters in the population
bias
systematic discrepancy between estimates and the true population characteristics
volunteer bias
volunteers for a study are likely to be different on average from the population
2 main goals of estimation
Accuracy - on average gets correct answer
Precision - repeatedly gives a similar answer
Random sample
each member of a population has an equal and independant chance of being selected
independant sampling
change of an individual being included in the sample does not depend on who else is sampled
sampling error
the difference between the estimate and average value of the estimate
We never know exact truth BUT we can compare to the average
Population parameters vs estimates
population parameters are CONSTANTS while estimates are RANDOM VARIABLES
error
a random difference (not tending in any direction) between an estimate and the true population characteristic
larger samples with have smaller sampling errors
