Statistics

Question 1

What analysis should you use of there is 2 categorical columns

Answer 1

odds ratio, g test or chi squared test

Question 2

What analysis should you use if there is one categorical column and 1 normal column

Answer 2

compare groups (groups in the categorical column)

Question 3

What analysis should you use if there are 2 normal columns

Answer 3

straight line, correlation OR repeated measures

Question 4

How can you choose between using straight line or correlation or repeated measures

Answer 4

You use a straight line or correlation when:

• The two columns seem to be very different kinds of things (age, blood pressure).
• When you might want to predict one column based on the values in the other (same).
• When you think these two different things might be related.

You use repeated measures when
* The two columns seem to be very similar kinds of things (stopping distances in wet, dry)
* When you’re interested in whether they are the same in some way.

Question 5

how can we tell if there’s any extreme values before using mean and median

Answer 5

use a histogram or boxplot of the data to see if there are any extreme values

Question 6

boxplot

Answer 6

The median (50% of the data is below the median, 50% above)
* The first quartile (25% of the data is below the 1st quartile value)
* The third quartile (75% of the data is below the 3rd quartile value)
* The Interquartile range (IQR) = 3rd quartile value – 1st quartile value.

Question 7

based on the box plot when should the mean and medians be used

Answer 7

mean can be used:
when the median line is in the middle of the box
the whiskers aren’t too long
there are no plotted points outside the whiskers

And also:
mean is similar to median

Question 8

paired measurements

Answer 8

occur when we take two or more measurements on a number of people. can analyse by looking at the distance between the two.

Question 9

what plot do we use for compare two groups

Answer 9

box plot

Question 10

what plot do we use for paired measurements

Answer 10

bland altman plot

Question 11

bland altman plot

Answer 11

horizontal black line is median of Y values

red line is at zero. if theres no difference the data should cluster around this

grey area should cover 95% of data points

Question 12

how to calculate odds ratio

Answer 12

probability event will occur over probability it wont

P/(1-p)

Question 13

analysing odds ratio

Answer 13

odd ratio of 1 indicates no relationship between rows and columns
odds ratio only works on tables with four cells