Experimental methods 1 of 12 Boardworks Ltd 2009

Experimental methods 1 of 12 © Boardworks Ltd 2009

Learning objectives By the end of this section students will be able to: Describe the scientific approach to the study of behaviour State the main features of laboratory experiments, field experiments, online experiments and quasi experiments. Evaluate each experimental method. Icons key: Flash activity (not editable) Web links 2 of 12 For more detailed instructions, see the Getting Started presentation Teacher’s notes (in Notes Page) Extension activity Sound Accompanying worksheet Video © Boardworks Ltd 2009

The experimental method All experiments are designed around the experimental method. It is a method used by scientists to test hypotheses. participants randomly allocated to conditions a change in the dependent variable, which is measured by the experimenter independent variable manipulated by experimenter extraneous variables are controlled Psychologists use three types of experiments to investigate behaviour: laboratory, field and natural experiments. 3 of 12 © Boardworks Ltd 2009

Laboratory experiment 4 of 12 © Boardworks Ltd 2009

Field experiment 5 of 12 © Boardworks Ltd 2009

Online experiments This is a new way of collecting data. Participants are collected through the internet or social media. Anyone can visit sites such as www. socialpsychology. org to become a participant; often taking part in questionnaires. Strengths Weaknesses • Access to a large group of ppts, meaning a diverse sample is collected that may be less culturally biased than if just undergraduates were used. • It is cost effective, often they can use free or cheap software. There is no need for a research assistant. Data analysis can also be quicker as ppts have already written their responses. 6 of 12 • Mostly the methods are questionnaires or surveys (and sometimes people lie on these – social desirability bias). • There are ethical issues such as consent, risk of harm and a lack of debrief to consider. Most users with tick a terms and conditions box without actually reading it. © Boardworks Ltd 2009

Quasi-experiments • There are two kinds of quasi-experiments: – Natural experiments (with an IV) – Differences studies (no IV) • You’ll now watch an animation on natural experiments and make notes in your booklet. 7 of 12 © Boardworks Ltd 2009

Natural experiment 8 of 12 © Boardworks Ltd 2009

Difference studies • The IV is naturally occurring and a DV can be measured in a lab. The IV has not been made to vary by anyone. • An example is studies of gender differences in obedience, or smelling (olfactory) abilities of sighted and nonsighted children. 9 of 12 © Boardworks Ltd 2009

Class discussion A psychologist wants to investigate the effect of chocolate on the performance of students. How could the psychologist test this? What variables need to be controlled? How could they be controlled? What experiments could be performed? Suggest laboratory, field and natural experiments he could perform. What are the advantages and disadvantages of each type of experiment? 10 of 12 © Boardworks Ltd 2009

Experimental Design Independent Groups Design Participants only take part in one condition of the experiment (2 Words separate groups) 2 1 Weaknesses: More ppts are needed than repeated measures design. Differences between participants in the groups may affect results, (participant variables). 1 2 Strengths: Avoids order effects. Less demand characteristics 11 of 12 Matched Pairs Repeated Measures Design Participants are Participants take part matched in each in both conditions of condition for the experiment (1 characteristics that group). may have an effect Pictures on their performance. 2 2 gender, IQ 1 1 age, e. g. Weaknesses: etc. Weaknesses: Very time-consuming trying to find closely matched pairs. Impossible to match people exactly. Requires more participants. Strengths: Reduces participant variables. Avoids order effects. Order effects are more likely to occur (counterbalancing needed). Demand characteristics more likely as participants might guess the aim of the study. 1 2 Strengths: Avoids the problem of participant variables. Fewer people are needed. © Boardworks Ltd 2009

Practice questions 1. Explain what is meant by independent groups design. (2) 2. Name one other type of experimental design and explain how it might be used. (2) 3. Explain one disadvantage of using matched pairs design. (3) 12 of 12 © Boardworks Ltd 2009