MEASURING THE DIFFERENCES BETWEEN PROPORTIONS CONFIDENCE INTERVALS

Question 1

Why present Confidence intervals

Answer 1

It measures the likely difference between proportions is probably more important

Question 2

If two groups are independant or unpaired what is required

Answer 2

The X2 test (chi squared test)

Question 3

What are the ways to measure confidence intervals?

Answer 3

1. ABSOLUTE DIFFERENCE
   D=π1-π2,
   R=π1/π2
   OR=(πr/(1-π1))/(π2/(1-π2))
2. THE RELATIVE RISK
3. THE RATIO

Question 4

What is the Null hypothesis

Answer 4

D=0, R=1, OR=1 are. all the same

Question 5

Can you work out the probability from the odds or visa versa

Answer 5

Yes the probability and odds of an event are EQUIVALENT ways of QUANTIFYING THE SAME DEGREE OF UNCERTAINTY: IF YOU KNOW ONE THEN YOU CAN FIND THE OTHER
For example:
If an event has probability π, then the same event has odds π(1-π) or π/(1-π)
So..
Probability of π=2/3 then odds is (2/3)/(1-2/3)=2.
Odds (n), the probability will be n/(1+n)

Question 6

What has the probability have to always been between

Answer 6

0 and 1

Question 7

What does odds have to be

Answer 7

Bigger than 0

Question 8

What is the 95% confidence intervals found as

Answer 8

D±1.96 x standard error

Question 9

What is the 99% confidence intervals found as

Answer 9

D± 2.58 x standard error

Question 10

Is there a connection between any odds ratio greater than one between two groups

Answer 10

Yes there is a connection between any odds ratio GREATER THAN ONE and its reciprocal, which is between 0 and 1

Question 11

Are all the values from 1 up to infinity equivalent to the values BETWEEN 0 AND 1 and does it give the distribution of the Odds ratio (OR) a natural skewness

Answer 11

Yes all values from 1 upto infinity are in some ways equivalent to the values between 0 and 1 GIVES DISTRIBUTION of the OR A NATURAL SKEWNESS

Question 12

How to work out the standard error of logOR

Answer 12

It is the SQUARE ROOT OF THE SUM OF THE RECIPROCALS OF THE ENTITIES IN THE 2X2 TABLE UNDERLYING THE RATIO

Question 13

What is the natural logarithm for OR

Answer 13

0.8019

Question 14

How to find the confidence intervals for the OR

Answer 14

Confidence intervals for the odds ratio (OR) is found by TAKING THE NATURAL ANTILOG OF THE VALUES (sometimes written as the EXPOTENTIAL of the values)

Question 15

Who do you find the mid-point inbetween the confidence intervals

Answer 15

You do 1/2 (first interval+ second interval)
This will be larger than the Odds Ratio (OR)

Question 16

Odds ratio (OR) =1 if….

Answer 16

The disease/condition/event is EQUALLY LIKELY to happen in exposed and non-exposed subjects

Question 17

Odds Ratio (OR) IS>1 if….

Answer 17

More likely to happen in exposed subjects

Question 18

Odds Ratio (OR) IS<1 or <0 if..

Answer 18

Less likely to happen in exposed

Question 19

What does Odds ratio (OR) equaling the difference in proportions or their ratios (RR) signify

Answer 19

The condition is rare

Question 20

How can confidence intervals be found

Answer 20

By getting Cl first for LOG OR and back transforming

Question 21

What do you need to use for Log OR

Answer 21

Natural logs

Question 22

What is logistic regression based on

Answer 22

The NATURAL LOG TRANSFORMATION (logit)

Question 23

What does the exponential logistic regression coefficient equal

Answer 23

The odds ratio