Statistics Flashcards
precision with which a characteristic is measured
scale of measurement
simplest level of measurement with qualitative/categorical observations described in proportions or percentages
dichotomous, binary
nominal
scale of measurement with inherent order among categories, the difference between 2 adjacent categories is not the same throughout the scale, described in proportions or percentages
ordinal
scale of measurement described with measure of central tendency and spread
continuous/numerical
arithmetic average used for numerical data sensitive to extreme values
mean
mean is best for what data
numerical, symmetric
50th percentile, arrange observations from smallest to largest and determine number of observations, for numerical and ordinal data
median
median is best for what data
ordinal or numerical, skewed
value occurring most frequently, used for numerical data to describe frequent observations in a large data set
mode
mode is best for what data
bimodal distribution
difference between largest and smallest observation
range
identify the 25th and 75th percentile and find the difference to find the
interquartile range
measures spread of data around the mean, statistic of interest, can determine skewness
standard deviation
a percentage of a distribution that is ≤ a certain number
percentiles
measures relative spread in data, used to compared variability across data sets, unitless
coefficient of variation
the area between the mean and 1 SD above or below the mean
data distribution
parametric tests assume data is
normally distributed
types of parametric tests
student’s t-test, ANOVA, ANCOVA
types of nonparametric tests
sign test, Wilcoxon rank-sum test, Mann-Whitney test, Kruskal-Wallis test, Spearman’s rank correlation
type of test used for non-normally distributed data, and for nominal and ordinal data
non-parametric test
type of distribution that applies only to continuous data achieved by picking subjects randomly, creating equal sample sizes, and obtaining large samples
normal (Gaussian)
type of distribution where data falls to the left or right of the mean
skewed
graphs for 2 characteristics for continuous data, every point is displayed, and displays exact distribution of the data
scatter plot
graph that shows continuous data that involved 5 values
min, 1st quartile, media, 3rd quartile, max
box plot (box and whisker plot)
graph that involves mean and SD data
error bar plot
graph where frequency is represented by bars, used with nominal or ordinal data, the measure of interest on the x-axis, number of percentage observations on the y-axis
histogram
line graph like a histogram used to compare 2 distributions on the same graph
frequency polygon
graph with sum of frequencies accumulated up to a specified boundary
cumulative frequency graph
a measure of the relationship between 2 numerical characteristics
correlation coefficient (r)
what do correlation coefficients -1, 0, and +1 say about the relationship
-1 = perfect negative linear
0 = no linear
+1 = perfect positive linear
describes the relationship between two ordinal characteristics, or 1 ordinal and 1 numerical
Spearman’s rank correlation
compares probabilities of developing an outcome in the presence or absence of a treatment risk factor
relative risk
compares odds of developing an outcome on the presence of a risk factor
odds ratio
comparison of hazard rates
hazard ratio
quantifies likelihood or benefit, # of patients needed to be treated to avoid 1 outcome
number needed to treat
refers to risk of detrimental effect, # of patients needed to be treated to cause an adverse event in 1 patient
number needed to harm