1. Research Methods
Lesson 2 Reliability

2. Lesson Objective Success Criteria
1.To understand what is meant by the term ‘reliability’.
To apply your knowledge of internal and external reliability to your cookie experiment.
To create a revision grid that looks at three methods to assess reliability.
Identify a method you could use to improve your reliability.
3. Challenge-: Apply your knowledge by completing question 1 (pg. 134) ; Practice for novel scenarios.

3. What would happen if?
The two brands of cookie got mixed up?
If one participant had forgotten their glasses?
If some cookies in one packet had melted?
If you used different tasting scales.

4. Reliability
The reliability of any method of measurement (this can be an interview, questionnaire, experimental test, etc) refers to how consistently it measures something. A reliable test gives similar results in similar circumstances. For example, if your kitchen scales gave you different readings each time you weighed out the same amount of sugar for your cake, they would not be reliable (neither would your cakes!).

5. Internal Reliability
How consistently a method/test measures within itself. . For example, if my 6 inch ruler had different size inches all the way along its length, it would not be standardised and would not have good internal reliability. Also, internal reliability would be bad if two people simultaneously observing the same participant’s behaviour scored it differently.
How can we make sure our cookie experiment has internal reliability?

6. External reliability
How consistently a method/test measures over time when repeated. A method/test with good external reliability will give similar scores for the same people under similar conditions. For example, if my ruler found different lengths each time it measured the same object, it would not have good external reliability.
How can we make sure our cookie experiment has external reliability?

7. Ways of dealing with issues of reliability
If there is a problem with reliability, for example, a question on a questionnaire turns out not to be consistent the psychologist can remove the item from the questionnaire or checklist and check to see if there is a correlation between the remaining items.

8. Methods used to assess reliability
There are a few techniques that psychologists can use to assess whether their experiment or research has high reliability. Complete the table to learn about these techniques: page 134
Inter-rater reliability
Test-retest reliability
Split-half reliability
A test of reliability for observers
A test of external reliability
A test of internal reliability

9. Methods used to assess reliability
There are a few techniques that psychologists can use to assess whether their experiment or research has high reliability. Complete the table to learn about these techniques:
Inter-rater reliability
Test-retest reliability
Split-half reliability
A test of reliability for observers
A test of external reliability
A test of internal reliability
Is measured by correlating the observations of two or more observers.
Is a measure of consistency over several different occasions.
Is used to assess internal reliability. One group of participants is given a test once. The participants answers are divided in half and compared. The individuals scores on both halves should be very similar.

10. Which method could you use to improve reliability?