Sign Test

When are the three times when you use a sign test

1. When the investigation is a test of difference

2. When the data is nominal

3. When the experimental design is repeated measures (Same person tested twice) or matched pairs.

Explain the first stage of conducting a sign test

Figure out what type of hypothesis it is:
- Directional hypothesis- one tailed test

Non directional- two tailed test

Explain the second stage of conducting a sign test

Record the data and work out a sign- - for one side and a + for the other- for example, a minus for unhappier and a plus for happier

Explain the third stage of conducting a sign test

Find the calculated value (S)- this is the symbol for the test statistic we are calculating. To calculate- add up pluses and minuses and selecting the one that appears the least.

In the table above there are 10 pluses and 3 minuses so the calculated value is 3.

Explain the fourth stage of conducting a sign test

Find critical value of S:

Step 1:

• N= total number of scores (ignoring any zeroes)= 13 for this study. (look back at picture on slide 3 or page 202 of book 1

Step 2:

• Now we look at table of critical values- it is a directional hypothesis so it is a one tailed test. Locate the 0.05 value amnd match it up to 13, so it is three.

• As a rule of thumb, use the number on the left, so 0.05 or 0.10.