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PSYCHOLOGY (paper 2) > inferential statistics > Flashcards

inferential statistics Flashcards

1
Q

what are inferential statistics?

A

they tell us the probability that data/results could have occurred due to chance rather than our manipulation

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2
Q

what are statistical tests used for?

A

to infer whether the findings are
true for a wider population

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3
Q

what are descriptive statistics?

A

when one number is used to describe your data (measures of central tendency, measures of dispersion)

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4
Q

what is probability?

A

the likelihood that a particular event (or outcome) will occur

(p)

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5
Q

what are the different hypotheses?

A

-directional (one tailed)
-non-directional (two-tailed)
-null (no-tailed)

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6
Q

what is a directional hypothesis?

A

a hypothesis that states the direction of the difference or relationship between variables

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7
Q

what is a non-directional hypothesis?

A

a hypothesis that does not predict the direction of the difference or relationship between two variables

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8
Q

what is a null hypothesis?

A

it predicts that a statistically significant effect or relationship will not be found

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9
Q

hypotheses & stats test:

A

-a statistical test determines which of the hypotheses are likely to have occurred by chance
-this results in either accepting or rejecting one of the hypotheses

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10
Q

what does a stats test not tell us?

A

how sure of our results we should be

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11
Q

what is significance?

A

a statistical term that indicates that the research findings are strong enough to let the researcher
reject the null hypothesis and accept the alternative/research hypothesis

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12
Q

what does it mean if the result of a statistics test are significant?

A

the results were unlikely to have occurred by chance, they are probably due to the independent variable

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13
Q

what is a level of significance?

A

the level of probability at which it has been agreed to reject the null hypothesis or accept the alternative hypothesis

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14
Q

which level of significance do psychologists use?

A

-psychologists can never be 100% certain about results as they have not tested all members of the
population under all possible circumstances
-this is why they settle for the 5% level

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15
Q

what does the 5% level of significance mean?

A

this means there is a 5% likelihood that the results have occurred by chance / it means that we can be 95% confident that the results
are due to the Independent variable

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16
Q

what is the most commonly used level of significance in psychology?

A

p = 0.05

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17
Q

how can probability be expressed?

A

as a proportion - eg: a 1 in 20 chance

as a percentage - e.g. a 20% chance

as a decimal - e.g. a probability due to chance of 0.2

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18
Q

> means

A

greater than

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19
Q

< means

A

less than

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20
Q

≤ means

A

the value is less than or equal to

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21
Q
A
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22
Q

what does p> 0.05 mean?

A

the probability that the results are due to chance is greater than 5%

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23
Q

what does p≤ 0.02 mean?

A

the probability that the results are due to chance is equal to or less than 2%

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24
Q

how can probability be expressed?

A

as a proportion - a 1 in 20 chance
as a percentage - e.g. a 20% chance
as a decimal - e.g. a 0.2 chance

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24
Q

what does p ≤ 0.01 mean?

A

the probability that the results are due to chance is less than or equal to 1%

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25
Q

what does p ≥ 0.05 mean?

A

the probability that the results are due to chance is greater than or equal to 5%

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26
Q

what does p ≥ 0.04 mean?

A

the probability that the results are due to chance is greater than or equal to 4%

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27
Q

what does p ≤ 0.001 mean?

A

the probability that the results are due to chance is less than or equal to 0.1%

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28
Q

when are stricter levels of significance used?

A

-sometimes we want to be more certain than 5%
-this may occur when there is a human cost (drug trials, or one off studies where the conditions could not be replicated again)

this level becomes 0.01 or 1%

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29
Q

what does a 0.01 level of significance mean?

A

there is a 1% likelihood that the results have occurred by chance /
we can be 99% confident that the results are due to the Independent variable

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30
Q

how is a 0.01 level of significance expressed?

A

p ≤ 0.01 (probability that results occurred by chance is less than or equal to 1%)

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31
Q

what happens a level of significance has been selected & a statistical test has been carried out?

A

the researcher has to decide whether to accept

the alternative hypothesis
(the effect has happened) or

the null hypothesis (there has been no effect/any effect observed is likely to have occurred by chance)

32
Q

what is a type 1 error?

A

where the null hypothesis is rejected and the alternative is accepted when it should be the other way around (LENIENT)

(optimistic error / false positive)

33
Q

what is the effect of a type I error?

A

the researchers claim to have found a significance difference when there is not one

34
Q

what is a type II error?

A

the null hypothesis is accepted and the alternative rejected when it should be the other way around.

(pessimistic error / false negative)

35
Q

what is the effect of a type II error?

A

the researchers claim there is
no significant difference between variables when there actually is one

36
Q

when are researchers likely to make a type 1 error?

A

the level is too lenient (0.1 or 10%)

37
Q

when are researchers likely to make a type 2 error?

A

if the level is too strict (0.01 or 1%)
→ this is why psychologists work at the 0.05 or 5% level to balance this chance risk of making errors

38
Q

what is the point of a stats test?

A

it will tell us the probability that our results arose due to chance alone

39
Q

which statistical tests do I need to know?

A

-sign test
-spearman’s rho
-pearson’s rho / pmc
-wilcoxon
-mann-whitney U
-related t-test,
-unrelated t-test
-chi-squared test

40
Q

calculations vs identification of tests:

A

-only be asked to calculate sign test
-for other tests, need to know when to use and why

41
Q

which areas need to be considered to choose the right test?

A

1) is it a test of difference or correlation?

2) which experimental design has been used?

3) what level of data has been used?

42
Q

how to identify a test of correlation?

A

-normally the stimulus material will mention words like ‘relationship’, link’, ‘association’
-there will never be any mention of conditions or experimental designs

43
Q

how to identify a test of difference?

A

-the material may mention words like ‘cause and effect or difference’
-they will be trying to find the difference between two groups response to the same variable
-there may be one or more groups of ppts and one or more conditions.

44
Q

what are the three types of experimental design?

A

-independent groups
-repeated measures/matched pairs

45
Q

independent groups:

A

there are different groups that participate in each condition

46
Q

repeated measures:

A

the same people complete the different conditions

47
Q

matched pairs

A

different participants complete each condition but they are matched based on key characteristics

48
Q

what are levels of measurement?

A

-when quantitative data is collected by a psychologist during research,
the information collected varies in how precise it is
-levels of measurement refers to these differences in precision

50
Q

why is it important to assess levels of measurement?

A

It is important to assess the level of measurement of a set of data because this will determine how it can be analysed statistically

51
Q

what are the three types of data?

A

-nominal
-ordinal
-interval

52
Q

nominal data:

A

-most basic level of measurement
-used when data is put into tally
charts/categories (categorical data)
-gives very little information – it only
tells us how many people are in
each group
-discrete data

53
Q

ordinal data:

A

-used when data is ordered / scaled
-the units of measurement aren’t equal
-usually based on opinion, tend to be subjective

54
Q

interval data:

A

-most complex level of measurement
-has an equal gap between each unit of measurement (fixed units)
-most objective and scientific of all data

55
Q

nominal data
(measure of central tendency +
measure of dispersion)

A

measure of central tendency -
mode (most popular category)

measure of dispersion -
X

56
Q

ordinal data
(measure of central tendency +
measure of dispersion)

A

measure of central tendency -
median

measure of dispersion -
range

57
Q

interval data
(measure of central tendency +
measure of dispersion)

A

measure of central tendency -
mean

measure of dispersion -
standard deviation

58
Q

DRAW OUT THE TREE DIAGRAM OF THE STATISTICAL TESTS

A
59
Q

a psychologist decided to design an experiment to test the effects of recreational screen time on children’s academic performance. the psychologist randomly selected four schools from all the primary schools in her county to take part in the experiment involving year 5 pupils. three of the four schools agreed to take part. in total, there were 58 pupils whose parents consented for them to participate. the 58 pupils were then randomly allocated to group A or group B.

for the two-week period of the experiment, pupils in group A had no recreational screen time. pupils in group B were allowed unrestricted recreational screen time. at the end of the experiment, all pupils completed a 45 minute class test, to achieve a test score.

the psychologist wanted to test the statistical significance of the data.

identify the most appropriate choice of statistical test for analysing the data collected and explain three reasons for your choice in the context of this study.

A

it’s a test of difference as the study intends to find the difference between the test scores with and without recreational screen time.

it’s an independent groups design as group A and group B each are in different conditions (unrestricted recreational screen time and no recreational screen time), they stay in these conditions.

there is interval data as the test scores of the 45 minute test have standardised / fixed units.

this means that the independent
t- test is most appropriate.

60
Q

what do you do with the results of a
stats test?

A

we compare our calculated value (the result from the statistical test) to a critical value to work out whether the result is significant or not and which hypothesis to accept

61
Q

in order to work out the correct critical value we need to know three pieces of information…

A

1) one or two tailed test? – was the hypothesis directional or non directional?

2) the number of ppts – usually the N value / degrees of freedom (df))

3) the level of significance (p value) usually as 0.05 (5%)

62
Q

what can be done once the critical value is found?

A

-it is compared against the calculated/observed value
-in some tests, our calculated value must be higher than the critical value, in others it must be lower
-if the critical value meets the conditions, the alternative hypothesis can be accepted

63
Q

DO SOME PRACTICE QUESTIONS IN PSYCH FOLDER

A
64
Q

what is the sign test?

A

a statistical test of difference
that allows a researcher to determine the significance of their investigation

65
Q

when is the sign test used?

A

in studies that have used a repeated
measures design, where the data collected is nominal and the experiment is looking for a difference

66
Q

how to DO a sign test:
(steps)

A

step 1 - state your hypothesis
-state whether condition A will do better/worse than condition B
-if we state a directional hypothesis then we require a one-tailed test,
-if we state a non-directional hypothesis then we require a two-tailed test)

step 2 - record the data and work out the sign
-record each pair of data (condition A vs B) from each participant
-write the difference between the data of each participant from each condition
-state whether the difference is positive (+), negative (-) or non existent (=)

step 3 - find the calculated value
-calculate the value of S (S is the symbol for the sign test)
-add up the total number of pluses and minus and select the smaller
value (EXCLUDE THE RESULTS THAT STAYED THE SAME)
-S = the smallest value (this is the calculated value)

step 4 - find the critical value

there are a number of things we need to know before we can find the critical value…
-the value of N (number of participants - number of 0)
-whether the hypothesis is directional (one-tailed) or non-directional (two-tailed)
-the significance level desired
(use a critical value table to find the critical value)

step 5 - conclusion
-for the sign test, the calculated value must be equal to or less than the critical value for the result to be significant
-if this is so, then we can accept our experimental hypothesis and reject the null hypothesis

67
Q

the psychologist obtained the following results:

-for two of the prisoners the number of aggressive acts increased
-for eight of the prisoners the number of aggressive acts decreased
-for two of the prisoners the number of aggressive acts stayed the same

the psychologist decides to use a sign test to see if his data are significant.

what is the calculated value of the sign test? explain your answer.

A

S = 2
this is because there are 2 of the least occurring sign, excluding those who stayed the same

68
Q

An experiment was conducted to investigate the effect of word length on recall in STM. In one condition, the participants were asked to call short words and in another the same participants were asked to recall long words.

A

A related t test should be used. The experiment is looking for the difference between recall of long words and the recall of short words. The experiment uses a repeated measures design as the participants participate in two conditions. Lastly,
experiment produces interval data, ad the participants recall can be scored using standardised units.

69
Q

A study was conducted to investigate whether there are gender differences in food preferences. Males and females were asked to choose whether they prefer chocolate or crisps.

A

A chi-squared test should be used. The study is looking for the difference between gender preferences towards chocolate and crisps. The results produce nominal data. Independent groups design has been used as the participants were either male.

70
Q

A study to investigate the relationship between students’ ratings of their own memory ability (out of 10) and their scores on a memory test.

A

The study is trying to find the correlation between the students ratings of their own memory (out of 10) and their scores on a memory test. The scores of a memory test produce interval data as it can be measured with standardised units. The statistical test would be Pearson’s.

71
Q

An experiment to see whether alcohol leads to slower reaction time. Half of the participants were given a drink containing 2 units of alcohol and the other half were given a drink with no alcohol. They were then timed to see how many seconds it took them to click the mouse when a red cross appeared on the computer screen.

A

Unrelated T Test.
The study is looking for a difference in reaction times with and without alcohol. An independent groups design is used as the participants only take part in one condition. The study produces interval data as time is measured in seconds (standardised units).

72
Q

A study to see if there is a correlation between the age of a child (in months) and the time taken to complete a maze.

A

Pearson’s Product Moment Correlation.
The experiment is looking for a correlation between the age of a child and the time taken to complete a maze. The data produced is interval as the time taken to complete a maze can be measured in seconds (standardised units).

73
Q

A study to investigate whether infants who are first born are more likely to be securely attached than infants who have older siblings. The infants were assessed using the Strange Situation and categorised as either being securely attached or insecurely attached.

A

A chi-squared test.
The study is looking for the difference between attachment types of first horns and children with older siblings. Independent groups design as each child is either first born or has older siblings. The data is nominal as the infants are categorised into attachment types.

74
Q

A study to investigate whether smokers are more likely to give themselves a higher rating for being impulsive than non-smokers.

The psychologist used a Mann-Whitney U test to analyse the data. With reference to levels of measurement, explain why this is a suitable test to use for this data.

A

Ratings don’t have standardised units, therefore they produce ordinal data.

75
Q

A study to investigate whether older people (35 to 70) are more likely to smoke that younger people (16 to 34).

A chi-squared test was used to analyse the data. With reference to levels of measurement, explain why this is a suitable test to use for this data.

A

The study produces nominal data, as each participant either fits into the category of more likely or less likely to smoke

76
Q

A psychologist investigated whether room temperature affects learning. Half of the participants learned and recalled the words in a warm room, and half learned and recalled them in a cool room.

The psychologist used a Mann-Whitney U test to analyse this data. Explain why a Mann-Whitney U test is an appropriate test to use and a Spearman’s rho test is not.

A

Spearman’s Rho is used if the psychologist is looking for a correlation, however, in this study, the psychologist is investigating the difference between learning and recall in a warm room and cool room. This means the Mann Whitney U test is appropriate.

77
Q

A psychologist investigated whether hunger affects concentration. Participants were timed to see how long it took them to find all the errors in a paragraph of text. Half of the participants did this shortly after eating their lunch. The other half completed the task 5 hours after they had last eaten.

The psychologist used an independent t-test to analyse the data. Explain why an independent t-test is an appropriate test to use and a related t-test is not.

A

The psychologist used an independent groups design, this means that the participants in each group only participated in one condition. While Independent T-Tests are used for an independent groups design, Related T-Tests are used during a repeated measured design.

78
Q
A

PSYCHOLOGY (paper 2) (19 decks)

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