vocab definitions Flashcards
sample of convenience
a collection of individuals that happen to be available at the time
variable
a measured characteristic on individuals from a population under study
data
measurements of one or more variables made on a collection of individuals
explanatory variable
a variable we use to predict or explain a response vairable
response variable
a variable that is predicted or explained from a explanatory variable
populations
a group of all individuals or groups that you want to study
sample
a subset ideally randomly chosen from a population you wish to study
parameters
things we want to know about the population
estimates
are calculated from a sample to help understand perameters
bias
a systematic discrepancy between estimates and the true population characteristic
volunteer bias
volunteers for a study are likely to be different on average from the poulation
sampling error
chance difference from the truth
precision
the spread of estimates resulting from sampling error
-gives a similar answer repeatedly
accurate or unbiased
the average of estimates that are obtained is on the true population value
-accuracy (on average gets the correct answer
random sample
in a random sample each member of a population has equal and independent chance of being selected
categorial variables (attribute or qualitative variables)
describe membership in a category or group
numerical variable
when measurements of individuals are quantitative and have magnitude. numbers
continuous
numerical data that can take on any real-number value within some range. Between any two values of a continuous variable, an infinite number of other values are possible.
discrete
numerical data that come in indivisible units. Example: number of amino acids in a protein and numerical rating of a statistics professor in a student evaluation are discrete numerical measurements
frequency
the number of observations having a particular value of the measurement
frequency distribution
shows how often each value of the variable occurs in the sample.
The frequency distribution describes the number of times each value of a variable occurs in a sample
independence
two events are independeent if the occurance of on egives no info about whether the second will occrur
multiplication principle
if two evens A and B are independent, then Pr[A and B] = Pr[A] xPr[B]
The addition principle
If two events A and B are mutually exclusive, then Pr[A or B]= Pr[A] + Pr[B]