Correlations Introduction Learning Objectives Identify the

Correlations Introduction

Learning Objectives • Identify the features of correlations. • Outline differences between positive and negative correlations and no correlations. • Outline features of a correlation coefficient.

Key terms • Correlation • Positive correlation • Negative correlation • No correlation • Correlation coefficient

Correlations • Correlation: a measure of how strongly two or more variables are related to each other: • Height is positively correlated to shoe size • The taller someone is, the larger their shoe size tends to be. • Like Self Report and Observation, there is no manipulation of data, conditions or groups in correlations. • No IV or DV, just to co-occurring variables (co-variables). Stretch & Challenge: If there is no IV, what can’t we establish?

Correlations • Still use the sampling methods: – Volunteer, self selected, random, snowball • Still consider the same ethical issues: – How many of the ethical issues can you identify? Give an example of how each ethical issue may need to be considered in a correlation.

• Unlike experiments there is no IV, just two variables that occur together as ‘co-variables. ’ • As there is no IV to manipulate we cannot establish cause and effect. • We don’t know which variable is causing the other, we just know there is a relationship between them. Experiment IV DV CAUSE EFFECT

• Unlike experiments there is no IV, just two variables that occur together as ‘co-variables. ’ • As there is no IV to manipulate we cannot establish cause and effect • We don’t know which variable is causing the other, we just know there is a relationship between them. Correlation Co. V ? Co. V NO CAUSE & EFFECT

• Correlations can be both the primary method or secondary technique. • Self reports and observations can both be used as a Primary method: Correlations way to gather data on variables, and then see if there is a relationship between them. • Experiments can compare the data between two groups using correlations. • I find out men have a stronger correlation between age and time spent looking in the mirror than women. Secondary technique: Self report/Observation Primary method: Experiment Secondary technique: Correlation Stretch and Challenge: which core study uses experiment as the method and correlation as the technique?

Task • Activity 1: Identify other possible correlations we could investigate for age and sleep. • Extension: Identify any two variables you would find interesting to investigate (you will be expected to conduct your own investigation at a later stage).

Positive and negative correlations • Positive Correlation: as one variable increases, so does the other. • Negative Correlation: as one variable increases, the other decreases. • No Correlation: there is no relationship between the variables. Stretch and Challenge: The more revision is done, the higher the final grade is. Is this a positive or negative correlation?

Positive, negative and no correlations – Activity 2 • Perfect Positive Relationship • No relationship • Perfect Negative Relationship

Correlation Co-efficient • We can measure the strength of the relationship, by using inferential statistics. • Which statistical test would we need to use? Why? • Being wealthy is correlated with living longer, BUT eating healthily and exercising has a stronger relationship with living longer. • Correlation Coefficient: a number between -1 and 1 that tells us how strong the relationship is.

Correlation Co-efficient +1. 0 perfect positive correlation +0. 8 strong positive correlation +0. 5 moderate positive correlation +0. 3 weak positive correlation 0 no correlation -0. 3 weak negative correlation -0. 5 moderate negative correlation -0. 8 strong negative correlation -1. 0 perfect negative correlation

Task • Complete Activity 3 in the workbook. • Calculate the co-efficient for the data sets given. • What can we conclude from the correlation co-efficient from this data?

Correlations Scatter diagrams and Evaluations

Learning Objectives • Identify the features of scatter diagrams. • Outline the different correlation hypotheses. • Evaluate the strengths and weaknesses of correlations.

Scatter diagrams • We can display correlation data in scatter diagrams. • One variable (amount of revision done) along one axis and another variable (final grade) along the other. • Each ‘point’ on the scatter diagram represents one participant: how much revision they put in and what their final grade was.

Amount of revision (in hours) Grade achieved A*-U Amount of revision (in hours) 0 2 5 7 10 Final grade U E C B A*

Amount of revision (in hours) Grade achieved A*-U • We can then use the scatter diagram to describe the relationship between the variables

Task • Complete Activity 4 in the workbook. • Plot one variable on the x axis and one on the y axis. • Plot using dots or crosses. • Remember to include: Title Clearly labelled both axes (including measurements when possible).

Hypotheses • Unlike Observation and Self Report we can generate hypotheses for Correlation Research. • Recap: Null Hypothesis Alternate hypothesis (one tailed or two tailed). What is the difference between a one tailed and a two tailed hypothesis?

Hypotheses • Correlations can’t show cause and effect • Can’t mention the effect one variable will have on the other so we talk about the ‘relationship’ between two variables • Still using the term significant • Still must clearly state the variables and how they have been operationalised • NEVER using the words cause, effect or difference.

Hypotheses • Null hypothesis: there will be no relationship • There will be no significant relationship between V 1 and V 2. Alternate hypothesis: One tailed: There will be a significant positive/negative relationship between V 1 and V 2 Two tailed: there will be a significant relationship between V 1 and V 2. Which word(s) must you NEVER use in a correlational hypothesis?

Assessment Tasks • Activity 5 - Complete the hypotheses questions in the workbook. • Activity 6 - Answer the sample exam questions relating to correlations.

Evaluation • Our correlation shows that ice-cream sales are positively correlated with murder rates. • Do we think buying ice-cream causes people to commit murder? • What third factor might make people more likely to buy ice creams and more likely to be angry and get in fights? • Why would it be a problem not to consider alternative variables? • Where in society do we tend to see correlationships described in causal terms?

Task • Complete Activity 7. • Mexican lemon imports prevent highway deaths • Eating organic food causes autism • From the buzzfeed article explain the correlations such as those above.

Strengths of Correlations Makes a good pilot study to generate a hypothesis for an experiment. ü Can research variables that would be unethical to manipulate. ü Can understand the relationship between two variables (positive/negative, weak/strong).

Weaknesses of Correlations do not show causation. They have the same weakness as whatever method was used to gather the data (observation/self report). Tell us nothing about other variables that may be the real cause Often correlations are misleading: NEVER USE DIFFERENCE, EFFECT OR CAUSE when describing a correlation.

Correlations Practical Activity

Learning Objectives • Carry out a practical activity on a correlation. • Write a report for correlational research.

Report Writing • You must complete a report for the correlation you have conducted • Remember the procedure must be replicable.

Task • You will now be carrying out your own correlational research. • Follow the instructions from Activity 8 in the workook. • You need to decide if you are using self report or observation to gather your data. • Make sure your data can be plotted on a scale, not qualitative or nominal.

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