Statistics equations

Question 1

What is the equation for standard error?

Answer 1

SD / square root of the number in the sample

Question 2

What are the equations for confidence level and power?

Answer 2

CI = 1 - alpha error
Power = 1 - beta error

Question 3

How do we transform, right skew left skew and exponential?

Answer 3

Right = square root or log
Left = square
Exponential = log or 1/x

Question 4

How do we calculate variance?

Answer 4

For each x:

(X-mean)2 / x-1

Question 5

How do we calculate standard deviation?

Answer 5

SD = square root of variance

Question 6

How do we calculate sensitivity, specificity, PPV and NPV?

Answer 6

All x 10p

Sensitivity = TP/ (TP + FN)
Specificity = TN / (TN + FP)
PPV = TP / (TP + FP)
NPV = TN / (TN + FN)

Question 7

What is the chi squared equation?

Answer 7

Sum of all:

(O-E)2 / E

Question 8

What are the equations for:
AR
ARR
NNT
RR
RRR
Odds
Odds ratio

Answer 8

AR = percentage chance of something happening = 1/10 or 10%
ARR = AR in control - treatment
NNT = 100%/ARR%
RR = treatment event rate/ control event rate
RRR = (CER - TER)/CER
Odds = number of events / number of non events
Odds ratio = treatments odds/ control odds