Stats Flashcards
Mean
Average add sum/number
Median
When is it preferred?
Rank lowest to highest
Middle value
Preff: in ordinal and continuous data
Mode?
Number than happens most frequently
Pref for nominal
Range?
Difference between largest and smallest
Normal distribution note
Mean median and mode are the same
Where do values fall in normal distribution?
68% within 1 SD
95% fall within 2 SDs
What is the possible error margin called?
APLHA
Alpha commonly set?
5%
When is the null rejected?
When the P-value is <0.05 if that is where the alpha is set
CI equation>
CI=1-a
If a CI contains what?
0 not statistically significant
FOR MEANS
Ration data? Three examples?
OD, HR, RR
CI confidence interval in ration data?
If it includes 1 not statistically significant
Type 1 errors? Also called?
Falso positive
Type 1 error in relation the H0 and Ha?
Alternative hypothesis was accepted and Null rejected in error
Type II is also called? How is it denoted?
False negative
B
Alternative was rejected and Null accepted in error
What is study power?
Probability that the test will reject the null correctly
How is power calculated?
1-B
RR values and interpretation? 3
=1 no difference
>1 greater risk of outcome in treatmetn
<1 lower risk in Tx
NNT NNH rounding
NNT anything greater than a whole number is rounded up to the next whole
NNH: anything greater than a whole number is rounded down
When is ANOVA used?
When using continuous data with 3 or more variables
T-Test
continuous data that is normally distributed
Student t-test: control versus placebo
Continuos data 2 tests
T-test and ANOVA
Discrete or categorical data test used? 1
Chisquared
Types of continuous data?
Ratio and Interval
Types of discrete or categorical data? 2
Nominal: arbitraty raking
Ordinal: ranked in logial order
Types of correlation tests?
Spearmans ranked order correlation
Pearsons correlation coefficient
What is the primary correlation test for continous data?
Pearson correlation coeffiecient
A test with 100% sensitivity?
Test will be positive in all patients who have the condition
Specifity
100% will be negative in all pts without the condition
What do forest plots do?
provife CIs for differnce data or ratio data
Forest plot interpretation
Vertical line is called the line of no effect set to zero for difference data and 1 for ration data
Hortizontal line is the length of the confidence interval
Case control study
What does it do?
Waht data?
Compared pts with a dx to those without
Retrospective
- ORs
Cohort study?
What data?
Compares outcomes of 1 group of pts exposed and not exposed
Prospective
or retro but less common
- OR
Cross sectional study?
What data?
Relationship at a point in time
variable and outcome at one point in time a CROSS SECTION
- p values
Cae report and case series?
What data?
Unique thing that happens in one patient or a few patietns
No statistical validity
RCTs
What data?
What data?
Compares control adn placebo
HR CI
Parallel RCT?
Randomized to tx and control for the entire study
Cross over RCT?
Randomised to one or two tx sequences
P values
Factorial design?
Randomized to more than the usual two groups
Meta analysis
Results from multiple study greatest signficantce power
sYSTEmmic review article?
Summary of lit that focuses on a specific question or topic
