Sampling General Population Representative Sample Generalisations Sampling Techniques Sample

20 psychology A-level learners 17 female 3 male   We want our research to apply to as many people as possible. We want to discover truths about all humans, not just the handful we experiment on. Target Population: The set of people researchers want to find out about. Sample: A small set of people taken from the target population. Target Population Sample Nurses 42 nurses from Daventry 39 female 3 male The Elderly 481 care home residents 481 male People 20 psychology A-level learners 17 female 3 male How representative are these samples?

Sampling bias Samples can be biased; they do not reflect the target population and this affects the conclusions we can draw from these samples. Gender bias: Sample is made of people from one gender, it is not representative of all genders. Androcentric: biased towards men. Estrocentric: biased to women. Cultural bias: Sample is too focused on one culture, isn’t representative of all cultures. Ethnocentric: biased towards one culture/ethnicity Population validity: Can we generalise results from our sample to the target population? Therefore, we need to be careful in selecting participants for our study. There are four different sampling techniques we use to do this.

Sampling Opportunity Sample People who are there at the time. Quick / Cheap / Easy Not representative Random Sample Each person in the GP has an equal chance of being chosen. Expensive and time consuming. Representative sample What kind of bias might there be?

Sampling Self-Selected What kind of bias might there be? What kind of bias might there be? Self-Selected Participants volunteer to be in the sample following advert etc. Quick / Cheap / Easy Not representative What kind of person volunteers for a psychology experiment? Snowball Sampling One person tells others who tell others … Allows us to collect difficult to locate people Time consuming

Hypothesis A hypothesis is a testable prediction of the outcome of an experiment. When we talk of more than one hypothesis, we call them hypotheses.   This is a key part of the scientific method in psychology. When a psychologist develops a theory, this needs to be tested. This is done by developing hypotheses and then carrying out experiments to test them. When we plan an experiment we make two predictions: The Independent Variable (IV) is going to affect the Dependent Variable (DV). This is called the Alternate Hypothesis. The Independent Variable is not going to affect the Dependent Variable. This is called the Null Hypothesis.

Operationalised hypotheses Operationalise means to put something into action. In relation to hypotheses it means that it is completely clear what the independent and dependent variable are. So for your IV, both conditions are clearly stated, and for your DV the measurement is clearly stated. For example “Caffeine affects memory” is a hypothesis, but it is not operationalised. Once we make it clear what the IV and DV are it would be operationalised. Sometimes you will be writing hypotheses for a study described in source materials. This is pretty easy to operationalise as you just have to identify the IV and DV in the source materials and transplant them into your hypotheses.

Experiments – Hypotheses How are we measuring memory? What’s better or worse? Higher / Lower? More / Less? Participants memory will be much worse when there is a distraction in the room than when there is no distraction. Participants memory will be much worse when there is a distraction in the room than when there is no distraction. What is the distraction? How are we manipulating it? Operationalising your hypothesis How have you manipulated your IV? How have you measured your DV?

Experiments – Hypotheses Participants memory will be much worse when there is a distraction in the room than when there is no distraction. Participants will remember significantly more words from a list of 20 presented for 60 seconds when they are in a room with no distractions than participants who are in a room where rock music is playing in the background.

A researcher is interested in whether caffeine affects memory A researcher is interested in whether caffeine affects memory. He gives one group of participants a can of coke then 30 minutes later he gives them one minute to learn a list of 15 everyday words and then sees how many they can write down. He repeats this procedure with a different group who are given caffeine free coke.

Types of alternate hypothesis One and two-tailed hypotheses There are two kinds of alternate hypotheses, a ‘one-tailed’ and ‘two-tailed’ hypothesis. One-tailed (directional) hypotheses: A one-tailed hypothesis predicts the direction of results. For example, “Participants who drink a can of coke will recall more words than participant who drink Caffeine free coke.” The word ‘more’, is predicting a particular direction. Two-tailed (non-directional) hypotheses: A two-tailed hypothesis, does not predict the direction of results. It just states that there will be an effect. For example, “There will be a difference in the number of words recalled by participants who drank coke compared to participants who drank caffeine free coke.” I generally prefer to write two-tailed hypotheses because you are ‘hedging your bets’. Maybe caffeine does improve memory (in which case I can accept the hypothesis) but maybe it makes it worse (in which case I can still accept the hypothesis!). Also it is very easy to turn it into a null hypothesis.

Experiments – Hypotheses Participants who [do something] will be significantly [faster/better/quicker etc] at [something] than participants who [do something else]. There will be no significant difference between participants who [do something] and those who [do something else]. Any difference will be down to chance. Alternative Null

Experiments – Hypotheses Participants who [do something] will be significantly [faster/better/quicker etc] at [something] than participants who [do something else]. There will be a significant difference between participants who [do something] and those who [do something else]. 1Tailed 2Tailed

Identify which of these hypotheses is one-tailed and which is two-tailed. a) ‘Leading questions affect memory of an event’.     b) ‘Taxi drivers will score higher on a memory test than non-taxi drivers’.   c) ‘Listening to music will increase your ability to learn information’. d) ‘Noise reduces concentration’.   e) ‘Watching TV affects aggressive behaviour’.

Experiment 1 A researcher is investigating how well Police officers recall number plates compared to non-Police officers by showing a slideshow of 10 number plates, then 5 minutes later they had to write down as many as they can remember. To get a point the number plate must be recalled exactly Experiment 2 A researcher is comparing the time taken to complete a lap of a driving obstacle course of male and female participants. Experiment 3 A researcher is comparing the number of guilty verdicts given in a mock burglary trial based on the area the accused is from. In one condition the defendant (an actor) has a Yorkshire accent and in the other condition the same defendant, in the same clothes, giving the same evidence, speaks with a Liverpudlian accent. Extension Does classical music improve learning? Identify the Iv and DV Write a one tailed alternate hypothesis Write a two tailed alternative hypothesis Write a null hypothesis