Specification: Aims: stating aims, the difference between aims and hypotheses. Hypotheses: directional and non‐directional. Variables: manipulation and control of variables, including independent and dependent.

Writing aims for investigations

Before a researcher considers the aim of the experiment, there is always a research question they are trying to answer. For example: ‘Does hunger affect memory for food‐related words?’ Thereafter, the researcher creates their aim: To examine the effect of hunger on memory of food‐related words.

Exam Hint: Always start the wording of an aim with ‘To examine the effect of…’

Identifying independent and dependent variables

The independent and dependent variables are the vital components of any experiment. Their presence is how you identify whether a study is following an experimental methodology or not. If there is no independent variable or dependent variable then the study is non‐experimental.

• Independent Variable (IV) – The variable that the researcher manipulates and which is assumed to have a direct effect on the dependent variable (DV).

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• Dependent Variable (DV) – The variable that the research measures. The variable that is affected by changes in the independent variable (IV).

Exam Hint: It is unlikely that you will be asked to define what is meant by the terms IV and DV. You are more likely to be asked to identify the IV and DV within a scenario.

For example: A psychologist showed participants 50 different cards, one at a time. Each card had two unrelated words printed on it, e.g. balloon or rabbit. Participants in one group were instructed to form a mental image to link the words. Participants in the other group were instructed to simply memorise the words. After all the word pairs had been presented, each participant was shown a card with the first word of each pair printed on it and asked to recall the second word.

What is the independent variable (IV) in this study? (2 marks)

Answer: Whether participants were instructed to form a mental image to link the unrelated word pairs or simply instructed to memorise the word pairs without a memory strategy.

What is the dependent variable (DV) in this study? (2 marks)

Answer: The number of word pairs correctly recalled by the participants in each condition.

Exam Hint: Before answering any question where you are required identify the IV and DV, read the extract carefully and underline the IV and DV. Once you have identified what you think the IV is, ask yourself the following question: “Is it possible for the experimenter to manipulate this variable?”. If your answer is ‘yes’ then this is likely to be your IV. If your answer is ‘no’ then this is unlikely to be the correct IV. 

There are two types of experimental hypotheses:

• Directional hypothesis: predicts the specific nature (direction) of the difference between two or more variables. This prediction is typically based on past research, accepted theory or literature on the topic. A directional hypothesis is sometimes called one‐tailed. Examples of key words used in a directional hypothesis are: higher, lower, more, less, increase, decrease, positive and negative.

Example: There will be a significant increase in the number of food‐related words correctly recalled by the participants who are hungry, in comparison with those who are not hungry.

• Non‐directional hypotheses: predicts that a difference will exist between two or more variables without predicting the exact direction of the difference. This is usually because previous research has been inconclusive, and the specific nature (direction) of the effect of the IV on the DV cannot be predicted confidently. Non‐directional hypothesis are sometimes called two‐tailed. The key word used in a non‐directional hypothesis is difference.

Example: There will be a significant difference in the number of food‐related words correctly recalled for participants who are hungry, in comparison with those who are not hungry.

Note: In the above non‐directional hypothesis, the IV (hunger levels) is shown to have an effect on the DV (number of food‐related words correctly recalled) BUT we have not said if the effect will be more/less.

Writing operationalised hypotheses for experiments

A hypothesis is a clear and precise prediction about the difference or relationship between the variables in the study. Operationalisation is the term used to describe how a variable is clearly defined by the researcher. The term operationalisation can be applied to independent variables (IV), dependent variables (DV) or co‐variables (in a correlational design).

The hypothesis should always contain an operationalised independent variable and dependent variable. For example, if the aim of a study was: to examine the effect of hunger on the memory of food‐related words, the IV is hunger levels (hungry vs. not hungry) and the DV might be the number of food‐related words correctly recalled.

Possible exam questions

1. Identify the directional hypothesis from the list below. (1 mark)

A There will be a difference in the driving ability of male and female drivers.

B There will be a relationship between number of hours sleep and concentration levels.

C There will be no difference between the amount of pasta eaten each month and ability to speak a foreign language and any difference seen will be due to chance.

D There will be a significant increase in the happiness rating of students who can leave lessons five minutes early each day compared to those who are kept behind.

2. A researcher is interested in studying the influence of caffeine on attention span through conducting a laboratory experiment. Identify the most likely independent variable (IV) for this investigation. (1 mark)

A Gender of the participant

B Ability to stay focused on a task

C Drinking a cup of coffee or a glass of water

D Location of the memory test

3. Suggest one reason why a psychologist might choose a non‐directional hypothesis over a directional hypothesis. (2 marks)

4. Explain the difference between a directional and a non‐directional hypothesis. (2 marks)

5. A psychologist is interested in studying the effects of staying up late and not getting the recommended eight hours sleep per night, compared to having an early night to get lots of rest on student performance in a maths test at school the next day.

   1. Identify the dependent variable (DV) in this investigation. (1 mark)

   2. What is the difference between an aim and a hypothesis? (2 marks)

   3. Explain what is meant by the term ‘operationalisation’. (2 marks)

   4. How does a researcher decide whether to select a directional or a non‐directional hypothesis? (2 marks)

6. A cognitive psychologist was interested in investigating whether memory for words presented with a visual representation alongside it, such as a picture, was better than memory for words presented alone. The researcher used an independent groups design with participants recruited through opportunity sampling at a university campus open day.

Group A: participants will be given two minutes to learn a list of 15 words before being asked to recall them freely in any order.

Group B: participants will be given two minutes to learn the same list of 15 words, but this time each word will presented with a visual representation alongside it. For example, the word ‘banana’ will have a picture of a banana next to it. Participants will then be asked to recall the 15 words freely in any order.

Suggest an appropriate non‐directional hypothesis for this experiment. (2 marks)

7. Research suggests that the cognitive interview technique can increase the accuracy of eyewitness testimony compared to the standard police interview. Lakin et al. wants to test the accuracy of eyewitness testimony following a real‐life bank robbery where staff and customers were held at gun point, to increase the chances of prosecuting the correct perpetrators. Twelve of the individuals present on the day of the crime agreed to take part in the study. The researchers decide to use an independent measures design.

Suggest a suitable hypothesis for this investigation. (3 marks)