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Psychology 1A > Experimental Design and Statisitcs > Flashcards

Experimental Design and Statisitcs Flashcards

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0
Q

Describe an Observational study

3 features

A

1) observe behaviour whilst it occurs naturally
2) descriptive method
3) can test hypotheses

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1
Q

What is a ‘variable’ ?

A

Any characteristic or factor that can vary

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2
Q

Issues with Observational studies (name 2)

A

OBSERVER BIAS - expectations of the observer & unconscious cues which influence the behaviour of P’s

REACTIVITY - change behaviour when we know we are being watched

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3
Q

How can we overcome issues with Observational studies?

OBSERVER BIAS

A
  • code procedures
  • make observers blind to hypothesis
  • use several observers and rate their consistency
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4
Q

How can we overcome issues with Observational studies?

REACTIVITY

A
  • use disguised observation for example two-way mirrors
  • get P’s used to the observer
  • use unobtrusive measures
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5
Q

What is a Correrlation study?

A

A relationship between two variables

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6
Q

Advantages of a Correlation study:

A

1) allows prediction

2) can study naturally occurring variables

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7
Q

Disadvantages of a Correlation study:

A

1) CANNOT establish a cause and effect relationship
2) third variable problem - unknown variable causing the change in the two variables rather than the variables themselves

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8
Q

What is an Experimental design?

A
  • investigates the effect of an independent variable on a dependent variable
  • variables are manipulated in a controlled setting
  • all other conditions remain constant
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9
Q

What is the independent variable?

A

The variable that the experimenter manipulates

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10
Q

What is the dependent variable?

A

The variable that the experimenter measures

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11
Q

What is a ‘between subjects design’ ?

A

When participants are assigned to different experimental groups

INDEPENDENT MEASURES

eg one group of students is assigned to teaching method A whilst another group is assigned to teaching method B

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12
Q

Advantages of a between subjects design

A
  • each P is naive to the experimental procedures

- essential when testing naturally occurring behaviours, eg gender

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13
Q

Disadvantages of a between subjects design

A
  • large number of P’s needed for each experimental conditions
  • individual differences eg personality traits
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14
Q

What is a “within subjects” design?

A

The same participants are tested under all the experimental conditions

REPEATED MEASURES

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15
Q

Advantages of a within subjects design

A
  • fewer P’s needed

- no individual differences since the same P’s are used for each experimental condition

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16
Q

Disadvantages of a within subjects design

A
  • order effects such as boredom or fatigue

* can stop this by using counterbalancing *

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17
Q

Define validity

A

Concerned with whether the method is measuring what it is supposed to be measuring

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18
Q

What is INTERNAL validity?

A
  • deals with what is going on inside the study

- the extent to which an experiment supports a clear causal conclusion - is the IV causing the changes in the DV?

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19
Q

What factors limit internal validity?

A

1) confounding variables
2) expectancy effects
3) external validity

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20
Q

What are confounding variables?

A

An extraneous variable whose presence affects the variables being studied so the results you obtain do not actually reflect the actual relationship between the variables under investigation.

21
Q

What are experimenter expectancy effects?

A

Subtle and unintentional cues which influence a P’s response

For example, an experimenter smiling when a participant behaves in the expected way

22
Q

What are demand characteristics?

A

Cues that the participants pick up about the hypothesis which influence their behaviour

23
Q

What is a placebo?

A

A substance with no pharmological effect

24
Q

What is the placebo effect?

A

A change in behaviour/symptoms due to expectations

Influenced by the colour of the pill, packaging and knowledge of the practitioner

25
Q

What are double blind studies?

A
  • both the P’s and experimenters are kept blind to the experimental hypothesis
  • this minimises the placebo effect as well as experimenter expectancy effects
26
Q

What is external validity?

A
  • the ability to generalise the findings of one experiment to other people and environments
  • replication
27
Q

What are descriptive statistics?

A
  • describes a set of data using specific measures

- summaries and describes characteristics of data

28
Q

What are inferential statistics?

A
  • allow us to make inferences about a population based on findings from a sample
29
Q

What is the mode?

A

The most common score in a set of data

30
Q

How do you calculate the mean?

A

The result of adding all the values of data together and dividing the total by the number of data points.

31
Q

What is the median?

A

The result when all the values in the data set are arranged in order and finding the middle value.

32
Q

Define a ‘population’

A

The entire group that is of interest to the researcher

33
Q

Define a ‘sample’

A

Subset of the population that the researcher is investigating

34
Q

What is a normal distribution?

A

Bell shaped curve

Defined by the mean and the standard deviation

35
Q

What is standard deviation?

A

Measures variation in terms of how far from the mean all the values in a sample fall.

36
Q

What does a large standard deviation value mean?

A

The data varies a lot

37
Q

What does a small standard deviation value mean?

A

The data varies a little

38
Q

What does a zero standard deviation value mean?

A

All the values in the data set are identical

39
Q

What does a t-test do?

A

Compares the differences between two samples or conditions

40
Q

What is a t-value?

A

A ratio of:

difference between means / variability about the means

41
Q

What does a large t-value mean?

A

The difference in means is large and the variability within the groups is low

42
Q

What happens if the t-value decreases?

A

As the differences in means decreases, variability increases

43
Q

What happens if the p value is < 0.05?

A

Reject the null hypothesis

44
Q

Which t-test should you use for a within subjects design?

A

Paired

45
Q

Which t-test should you use for a between subjects design?

A

Independent

46
Q

What is an independent t-test?

A

A parametric test which compares means from two different separate groups

47
Q

What do parametric tests do?

A

Make assumptions about our data

Eg - normal distribution, interval / ratio scale, homogeneity of variance

48
Q

What is a paired t-test?

A

A parametric test which compares means from the same sample tested under two different conditions

49
Q

When are non-parametric tests used?

A

When the data does not meet the assumptions of parametric tests - the data is not as distributed

50
Q

Describe the Mann-Whitney U-test

A

Rank scores from the lowest to the highest

See if a group has a consistently lower ranking

Calculate a U value and the p value

A significant p value is <0.05

51
Q

Describe the Wilcoxon Signed Ranks test

A

Calculate the difference between each pair of scores

Rank the difference scores are ranked from lowest to highest

Add together the ranks of the positive scores and the negative scores

The smallest value of the summed ranks = T value

A significant p value is <0.05

Psychology 1A (6 decks)

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