Aims and Hypotheses

Define ‘aim’

A clearly phrased general statement about what the investigator intends to research

*Can include the purpose of the study, for example, following on from findings of previous research to develop a theory or perhaps a direct replication. Phrased as either a question or a statement

*Eg “the aim of this research is to find out if colour can influence recall, due to previous research showing exposure to green plants increased recall”

Whats the difference between an aim and a hypothesis?

Aims say what the researcher is intending to investigate, and a hypothesis is formulated to communicate exactly how the research will be conducted

Define ‘hypothesis’

A precise testable statement including levels of the independent variable and dependent variable (or both covariables for a correlational study)

*Eg “there is a difference in the number of words recalled by participants recalling in blue light compared to participants recalling in green light”

What is operationalisation?

Operationalised variables are carefully stated, demonstrating exactly how they are to be measured eg the dependant variable would be the ‘number of words recalled’ not ‘recall’

What are some examples of operationalisation?

• Reaction time in milliseconds

• Average change in heart rate in beats per minute

• Average change in score on a hostility questionnaire

• Average shock level given to a confederate

How should the independent variable be phrased?

The independent variable needs to clearly state both levels so “participants recalling in green light and participants recalling in blue light” NOT “the colour of light” or “green light or not” or “condition A or B”

What is a null hypothesis?

States that there is no change (difference) in the measurement of the dependent variable as a result of the manipulation in the independent variable

What is an alternative hypothesis?

States that there is a change (difference) in the measurement of the dependent variable as a result of the manipulation in the independent variable

*Also known as the research hypothesis

Hypothesis testing…

Data is collected and statistical testing is conducted on the data. This provides evidence, if the evidence is strong enough the null hypothesis can be rejected and the alternative hypothesis is accepted

What are the 2 types of alternate hypothesis?

• Directional (one-tailed)

• Non-directional (two-tailed)

What is a non-directional hypothesis?

States that there is a difference in the measurement of the dependent variable (as a result of the manipulation of the IV) but not the direction the results will go

*Eg “there is a difference in the number of words recalled by participants recalling in green light compared to participants recalling in blue light”

What is a directional hypothesis?

States that there is a difference in the measurement of the dependent variable (as a result of the manipulation of the IV) and says which direction the results will go.

*Eg “there is an increase in the number of words recalled by participants recalling in green light compared to participants in blue light”

When should a researcher use a directional hypothesis?

A researcher should only use a directional hypothesis if there is previous research that suggests which way the results are likely to go

The importance of falsifiability!

Any theory, even well established theories backed up with a significant amount of prior evidence have to be open to the possibility that new research will emerge that contradicts its basic principles. The more a theory is able to withstand attempts to falsify it, the greater the confidence we have in that theory (but confidence can never be 100%)

Probability in psychological research!

As in experiments hypotheses are accepted or rejected on the basis of statistical testing, this means the strength of evidence is based on probability. In psychology, it is standard practice to accept results if the data passes a 0.05 level of significance. This means accepting that there is a 1 in 20 chance the results are a ‘fluke’