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RMA > descriptive statistics > Flashcards

descriptive statistics Flashcards

1
Q

what is a variable?

A

something that changes

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2
Q

what does operationalised variable mean?

A

specific statement about how a variable will be measured

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3
Q

what are the problems with defining variables?

A
  1. subjectivity vs objectivity
  2. testability
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4
Q

what are the 4 types of measurement

A
  1. nominal scales
  2. ordinal scales
  3. interval scales
  4. ratio scales
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5
Q

how do scales differ in relationship (2)

A
  1. the properties of the numbers
  2. the properties of what is being measured
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6
Q

what is a nominal scale?

A

numbers merely label

no relationship between number size and attribute measured

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7
Q

what is ordinal scale?

A

order of size of numbers = order of size of attribute measures

ordered

distance between scores vary

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8
Q

what is interval scales?

A

eqaul intervals on scale = equal intervals in property measured

measure magnitude

zero = no meaning

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9
Q

what is ratio scales?

A

interval scale AND zero means something

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10
Q

example of ratio scale

A

the time taken for ppt to press button

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11
Q

example of interval scale ?

A

degrees celsuis

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12
Q

example of ordinal scales?

A

IQ score

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13
Q

example of nominal scales?

A

numbers on buses

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14
Q

what are the measures of central tendency

A

mean

median

mode

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15
Q

what is the mean?

A

average

add all then divide by how many there is

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16
Q

what is the median?

A

midpoint of the sample after data has been put in order

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17
Q

when to use the mean?

A

if all values are important and valid

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18
Q

when to use the median?

A

if there are outliers

best choice for ordinal data

19
Q

what is the mode?

A

score that occurs the most

20
Q

when to use the mode?

A

nominal scale

can be bimodal (two)

21
Q

what are the limitations of using the mode?

A
  1. some data sets have no mode
  2. some data sets have more than one mode
  3. the mode can be atypical
22
Q

when can you use the mode (4)

A

nominal
ordinal
interval
ratio

23
Q

when can you use the median (3)

A

ordinal
interval
ratio

24
Q

when can you use the mean? (2)

A

interval
ratio

25
Q

what are 3 ways to measures of spread of data?

A
  1. range
  2. interquartile range
  3. standard deviation
26
Q

what is the range?

A

difference between highest and lowest number

27
Q

what is 1 problem with the range?

A

tells us nothing about the scores between the min and max scores

28
Q

what is the interquartile range?

A

measures the spread of the middle 50% of scores

between 1st and 3rd quarters

29
Q

what is standard deviation?

A

measure of variation around the mean

higher the SD = larger spread of scores.

30
Q

what does the standard deviation do?

A

gives an indication of what is happening between min and max of data set

31
Q

how to calculate the standard deviation?

A
  1. calculate the mean
  2. work out how far each score is from the mean
  3. square deviation scores
  4. sum this
  5. sum of scores / number of scores
  6. square root the variance
32
Q

what is it called when we mimic the mean in standard deviation

A

the variance

33
Q

what is a graph?

A

visual methods of representing data

34
Q

what do graphs do?

A

indicate patterns within the data

35
Q

why do we use graphs?

A
  1. decide how to analyse our data
  2. illustrate findings
36
Q

what are the 4 types of graphs?

A
  1. bar graphs
  2. stem and leaf plots
  3. box plots
  4. scatterplots
37
Q

what is a histogram?

A

type of bar graph

38
Q

what are stem and leaf plots?

A

data in a compact form

show size of data subsets

can have two digits

39
Q

what do box plots summarise? (5)

A
  1. lower and upper quartile
  2. median
  3. minimum
  4. maximum
  5. outliers
40
Q

what are scatterplots?

A

show the relationship between variables

41
Q

what are box plots good for?

A

comparing more than one data sets

42
Q

why are histograms and stem and leaf plots used? (3)

A
  1. show frequency of values
  2. show overall pattern
  3. spot outliers
43
Q

why are bar plots used?

A

data on nominal scale

44
Q

what must be done before running a statistical analysis?

A

data must be plotted

RMA (7 decks)

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