sign test

Question 1

recap

Answer 1

• Significance and probability
• Null and alternative hypotheses
• P=0.05
• 1 Tailed vs. 2 Tailed Tests
• Choosing a test
• Levels of measurement
• Related vs. Unrelated designs
• Critical and calculated values

Question 2

when to use sign test

Answer 2

• A test of difference
• Nominal data
• Related design

Question 3

Our experiment

Answer 3

-Work out difference between two sets of data eg depression score before and after therapy.

-Don’t need exact figures. + or - will do

-Doesn’t matter which column is subtracted from which

• Add up the total number of +’s and -‘s.
• += 5
• - = 3
• Where there is no difference the data can be ignored.
For all intents and purposes the participants are deleted.

• The less frequent sign is your S
value
• S = 3
• This is your calculated value.
• Your N value (participants) is the number of participants not including the 0 values.
• N=8

• Compare your calculated value (S=3) to your critical value.
• The critical value can be found in the critical values table, which will be given to you.
• Is your test 1-tailed or 2-tailed?
• 2-Tailed - non-directional hypothesis
• What is the significance level being used?
• P=0.05 as we haven’t been told anything different.
• How many participants are there?
• N=8

Calculated value S must be equal to or less than the critical value in order to be significant

The calculated value (S=3) is greater than the critical value of 0.
Therefore the difference in depression score before and after therapy is not significant.