Biostats 4 and 5 Flashcards
why are measures of centrality important
gives us a comparison point to use with a number we have
def. mean
sum of all data points/total number of data points
def. median
number where half the data points are above and half are below
def. mode
number that occurs most often
def. range
lowest to highest values
def. variance
direct measure of variability in the data - (sum of ((distance between each data point and mean)squared))/N-1
def. SD
square root of variance
def. interquartile rage
special rage that uses limits corresponding to 25th and 75th percentile
def. 95% CI
if you were to go back and sample the pop, then 19/20 times the score would fall within this range
CI formula
(mean - 1.96xSD, mean + 1.96xSD)
2 general types of research quesitons
- descriptive
2. hypothesis testing
def. DV
the outcome that is being measured
def. null hypothesis
that there is no change/diff between groups
def. alternative hypotheses
H1 or HA - that there is a difference
def. hypothesis testing
use of stats to determine if null can be rejected
when to use 2 vs. 1 tailed tests
2 - when we just want to show a difference
1 - when we expect to show a difference
def. type 1 error
alpha, usually set at 0.05 - falsely reject null hypothesis
def. type 2 error
beta, usally set at 0.2 - falsely accept the null hypothesis
def. power
1-B - the probablilty that the analysis will find a difference when a difference actually exists
def. p-value
probability that something occured by chance alone
