Sign Test

Question 1

What are the sign tests conditions?

Answer 1

We need to be looking for a difference (rather than a correlation or association) between two sets of data

We need to have used a repeated measures design

We need to have data that is organised into categories and every response can only fall into one of these categories (this is a type of data known as nominal data)

Question 2

What is the first step of the sign test?

Answer 2

The first step of the sign test is to enter a plus or minus sign to indicate the direction of difference.

increased +
Decreased -
same =

Question 3

What do you omit? (get rid of)

Answer 3

Omit any that stayed the same.

Question 4

How to get Sobs?

Answer 4

Which sign occurred the least number of times?
+
How many times did it appear?
4
This number gives us our observed value of S (or Sobs)
So here Sobs = 4

Question 5

What do you then compare?

Answer 5

We now need to compare Sobs to Scrit – the critical value we obtain from a sign test critical value table.

The critical value table will always be provided for you, but you need to know how to find the critical value from the table.

Question 6

What do you need to know?

Answer 6

You need to know:
Was H1 directional (one tailed) or non-directional (two tailed)

What the level of significance is

n (number of data sets) – remember some might be omitted

Question 7

If the observed value is SMALLER than the critical value then you

Answer 7

if the observed value is SMALLER than the critical value then you have a significant result, i.e. you can accept your hypothesis and reject the null.