CorrelationsPsychological Investigations

• Suzie’s goldfish lives in a tank on her desk. The more fizzy drinks she consumes, the more her fish swims around.

• Can we say there is cause and effect?

Goldfish and Fizzy Drinks..

Content Page SLIDES

1. Describe & Evaluate the Method

2. Hypothesis & Variables

3. Design n/a

4. Sampling Method n/a

5. Operationalisation & Measurement n/a

6. Reliability & Validity of measurement

7. Ethical Issues

8. Data (Graphical & Conclusions)

9. How would improve…?

10. Writing a Procedure

1. Description & Evaluation

Correlations

What is a correlation?

Strengths and Weaknesses

• Age affects a child’s ability to understand that volume stays the same even when shape changes.

• The duration of eye movements in sleep are related to the perceived the length of a dream.

• There is a link between the size of the hippocampus in the brain and a person’s navigational ability.

• Children are more likely to copy the behaviour of the same-sex adults than that of opposite-sex adults.

Relationship or Cause and Effect

1. Using clues within the sentences identify if it is a relationship or cause and effect relationship.

2. Underline the two variables within each statement.

EXT: If it is a relationship, what might be the third variable?

Types

Positive is the relationship between two variables such that an increase in one accompanies an increase in another. For example: There is a positive correlation between

students who revise more and high levels of achievement.

Negative is the relationship between two variables such that an increase in one accompanies a decrease in another.For example: There is a negative correlation between

the more you drive at night the less nervous you will be when you drive at night.

No Correlation is when there is no relationship between variables

• 1. The less aggressive a child is, the less physical force her parents are likely to use in disciplining her.

• The hotter the weather, the more crimes against people (mugging etc) tend to occur.

• The more you practice guitar playing, the less mistakes you make.

• The higher a male monkey’s testosterone level, the more aggressive he is likely to be.

Are the following correlations positive or negative?

EXT: Write your own positive and negative correlation.

2. Hypothesis

Correlations

Non Experimental Hypothesis

Definition A statement of the relationship between the two co-variables

Reasons for using

An alternative to the null hypothesis (accept/reject)

Null Hypothesis

Definition An assumption that there is no relationship in the population from which a sample is taken with respect to the variables being studied.

• Hypotheses for correlations are slightly different as they predict a relationship between 2 variables rather than a difference caused by an IV.

• This is a one-tailed hypothesis as the hypothesis predicts the expected direction of results.

• A two-tailed hypothesis which does not predict the expected direction would be ‘there will be a significant correlation between the size of a child’s feet and their score on a maths test.

• There also needs to be a null hypothesis.

• They must be operationalised: to make the variables measurable

Hypotheses for correlations

You want to see if there is a correlation between children's show size and academic ability.

• There will be a significant positive correlation between the size of a child’s feet ,measured in cm’s and their % score on a 10 question maths test.

• There will be a significant correlation between the size of a child’s feet ,measured in cm’s and their % score on a 10 question maths test.

• There will no significant correlation between the size of a child’s feet ,measured in cm’s and their % score on a 10 question maths test.

• Write an operationalised correlational hypothesis and a null hypothesis for an investigation into cognitive ability and alertness

• Correlational Hypothesis:

• Null Hypothesis:

Hypotheses for correlations

• Write an operationalised correlational hypothesis and a null hypothesis for an investigation into amount of sunshine and ice-creams sold

• Correlational Hypothesis:

• Null Hypothesis:

Hypotheses for correlations

Let’s go back to the correlation we conducted last lesson and construct a:

• One tailed hypothesis

• Two tailed hypothesis

• Null hypothesis

2. How strong the relationship is.

• What is a correlation coefficient? * This is a measure of the strength of the correlation.• Correlation coefficient can be calculated in a number of ways such as

with a Spearman Rho. This is one of the statistical tests that you need to know about at A2.

• If your design is a correlation, you always choose to use Spearman Rho as your statistical test.

* The closer the coefficient is to 1 or -1 the stronger the correlation

Perfect strong moderate weak no relationship

-1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 +1

What can correlations tell us besides that there is a relationship?

6. Reliability & Validity of Measurement

• Evaluate/Assess

• How could you assess

• How could you improve

Reliability: Consistency

Internal Reliability

Split-half method (questionnaire)Inter-rater )observation

External Reliability

Test-Retest (questionnaire)

Validity: The legitimacy of a study

Internal Validity

Demand Characteristics: Features of an experiment the elicit a particular response form participants.

Confounding variables affects the outcome of an investigation because it acts as an additional IV.

External Validity

Ecological validity: generalise from one setting to another

Population validity: generalise from one group of people to everyone

5. Validity of Measurement • Concurrent (pre-

established• Criterion (different

method)

6. Ethical Issues Deception Informed consent Psychological harm

Informed consent Difficulty debriefing Privacy

Confidentiality

7. Data

2. How strong the relationship is.

• What is a correlation coefficient? * This is a measure of the strength of the correlation.• Correlation coefficient can be calculated in a number of ways such as

with a Spearman Rho. This is one of the statistical tests that you need to know about at A2.

• If your design is a correlation, you always choose to use Spearman Rho as your statistical test.

* The closer the coefficient is to 1 or -1 the stronger the correlation

Perfect strong moderate weak no relationship

-1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 +1

What can correlations tell us besides that there is a relationship?

• Correlational analysis always involves quantitative data.

• When carrying out correlational analysis the data is summarised by presenting the data in a scattergram (or scattergraph). A scattergraph is a graph that shows the correlation between two sets of data (or co-variables) by plotting dots to represent each pair of scores. For each individual we obtain a score for each co-variable.

• It is important that the scattergram has a title and both axes are labelled. From the scattergram we may be able to say whether there is a strong positive correlation, a weak positive correlation, no correlation, a weak negative correlation or a strong negative correlation but we can not make a conclusion about the hypothesis.

Scatter Graphs

Parts of a Scatter graph

• Draw scatter graphs for the following:• Positive correlation

• Negative correlation

• No correlation

Scatter Graphs

How do the following Scatter graphs look?+1 Correlation

0.5 Correlation

-1.0

• Today we are going to test out whether there is a relationship between the number of hours you sleep and the amount of energy you have.

• Before we start what are the key words in the above statement?

Let’s try one….

EXT: What type of correlation would you expect?

Participant # of sleep # of Star Jumps you can complete

1

2

3

4

5

6

7

8

How to Record the Data?

Let’s Display our Data

8. How would you improve • Validity • Reliability • Ethics

9. Writing a procedure

June 2013Psychologists are interested in investigating if there is a

correlation between age and ability to use the internet.

• Describe and evaluate a way to measure ‘ability to use the internet’ that could be used in this study. (10)