Biostatistics I Flashcards
categorical vs discrete
categorical fits into natural categories and discretes are ordered numerical data
continuous
numerical data that can take on a continuous range of values
name 3 types of samples
sample of convenience, random sample and stratified sampling
stratified sampling
sample is drawn within each of two or more strata (groups with common characteristic). used to improve accuracy of results in certain circumstances
name 3 types of data variables
categorical, discrete (ordered numerical data restricted to INTEGER vales) and continuous (numerical data that can take on any value)
what are the 3 percentages for 1, 1.96 and 2.56 standard dev. of mean?
68%, 95% and 99%
how do you calculate the standard error of the mean?
s is standard error and n is smple size
how you calculate confidence interval?
x(x is the mean) ± (1.96)* (SEx, std err of mean)
in a distribution that is skewed to the left, which is greater, the mean or median?
median
in a distribution that is skewed to the right, which is greater, the mean or median?
mean
as sample size increases, what happens to the SE of the mean, width of CI and confidence level?
SE of the mean decreases, the width of CI decreases and confidence level stays at 95%
what is set (probability)
a collection of distict objet (e.g. a sample of patients)
what is ‘event’ (probability)
a characteristic defining a subset of our Set (e.g. affliction with a disease)
what is the equation for conditional probability
(E1 + E2)/(E2)
what is the general multiplication rule for dependent events
Pr(E1 and E2) = Pr(E1|E2) * Pr(E2)
