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Data Management > One-Variable Descriptive Statistics > Flashcards

One-Variable Descriptive Statistics Flashcards

1
Q

define population

A

the set of all objects being studied

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2
Q

give an example of population

A

studying bolts, the population is all bolts produced

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3
Q

define sample

A

a portion (subset) of the population

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4
Q

what should a sample be?

A

representative of the population

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5
Q

define data

A

information collected on a sample

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6
Q

two types of data

A

qualitative and quantitative

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7
Q

define qualitative data

A

information collected on a sample that is non numerical

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8
Q

give an example of qualitative data

A

hair colour

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9
Q

define quantitative data

A

information collected on a sample that is numerical

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10
Q

give an example of quantitative data

A

height

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11
Q

two types of quantitative data

A

discrete and continuous

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12
Q

define discrete quantitative data

A

numerical information collected on a sample that is whole numbers based on counts

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13
Q

define continuous quantitative data

A

numerical information collected on a sample that is real numbers based on measurements

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14
Q

give an example of discrete quantitative data

A

number of people in a class each day

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15
Q

give an example of continuous quantitative data

A

weight

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16
Q

4 levels of numerical data

A

nominal, ordinal, interval, ratio

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17
Q

define nominal data

A

numbers as labels, no numerical quantity

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18
Q

give an example of nominal data

A

numbers on sports jerseys

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19
Q

define ordinal data

A

quantities are placed in order like from smallest to largest

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20
Q

give an example of ordinal data

A

1st, 2nd, 3rd

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21
Q

define interval data

A

arbitrary starting point, differences between quantities have meaning

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22
Q

give an example of interval data

A

added or subtracted, not multiplied or divided, like temperature in celsius or farenheit

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23
Q

define ratio data

A

all mathematical operations have meaning, fixed starting point

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24
Q

give an example of ratio data

A

temperature in kelvins because it starts at absolute zero, a fixed starting point

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25
Q

two main types of descriptive statistics

A

graphical and numerical

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26
Q

define descriptive statistics

A

used to organize and summarize data in order to uncover trends, patterns, make estimates and inferences about the population

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27
Q

define graphical descriptive statistics

A

visual displays used to show trends or behaviour

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28
Q

give 4 examples of graphical descriptive statistics

A

tables, charts, graphs, plots

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29
Q

define numerical descriptive statistics

A

specific mathematical expressions computed using the sample values which describe some aspect of the population

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30
Q

6 examples of numerical descriptive statistics

A

mean, median, mode, range, standard deviation, line of best fit

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31
Q

two ways to order samples

A

notation and ordered

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32
Q

example of notation sample

A

x1, x2, xn

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33
Q

example of ordered sample

A

x(1) < x(2)

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34
Q

what do you have to include in stem leaf plots

A

the value of the stem and leaf

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35
Q

for the x interval in a frequency table, what do you have to include?

A

one has to be equal to or smaller/larger than x

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36
Q

what is frequency

A

the number of leaves in the interval

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37
Q

what is relative frequency?

A

the frequency over n

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38
Q

what is percentage?

A

the percentage of relative frequency

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39
Q

what is the cumulative frequency

A

add up frequencies cumulatively each time

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40
Q

in a histogram, what do you plot

A

frequency vs x interval

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41
Q

ways to describe a histogram

A

uni modal (one peak), gap, spread out

42
Q

when do you use histogram vs bar graph

A

quantitative vs qualitative

43
Q

in an ogive, what do you plot and what it looks like

A

cumulative frequencies over x interval; connected dots

44
Q

4 measures of central tendency (location)

A

sample mean (average), sample median, sample mode, percentiles

45
Q

what is the sample mean also called

A

arithmetic mean

46
Q

how to calculate sample mean

A

x bar = sum of x / n where x bar is between or equal to the minimum or maximum

47
Q

what is the sample median and its symbol

A

x with squiggle; the middle observation in an ordered sample

48
Q

what is the sample mode and its symbol?

A

most frequently occurring observation in the sample, mode is not unique, may have more than one mode (multimodal) or no mode at all, Mx

49
Q

shape of population distribution when mean is near median?

A

symmetrical

50
Q

shape of population distribution when mean is greater than the median?

A

skewed to the right

51
Q

on a population distribution, where is the mean?

A

on the lower side

52
Q

shape of population distribution when mean is less than median?

A

skewed to the left

53
Q

define percentile

A

the location in an ordered sample that is larger than that percentage of the observations

54
Q

which measure of location is a percentile and which percentile is it?

A

median is p50

55
Q

5 intervals for box and whisker plot

A

minimum, first quartile = p25, second quartile =median=p50, third quartile = p75, max

56
Q

when middle bar is closer to right and whisker is shorter, what is the shape of the population distribution for a box and whisker plot?

A

skewed to the right

57
Q

when middle bar is closer to the left and whisker is shorter, what is the shape of the population distribution for a box and whisker plot?

A

skewed to the left

58
Q

range on box and whisker plit

A

between min and max

59
Q

inter-quartile range for box and whisker plot

A

between first quartile and third quartile

60
Q

what does a box and whisker plot mean?

A

25% of the sample is between each quartile

61
Q

define range

A

the difference between the largest and smallest observations in a sample

62
Q

define the interquartile range

A

the difference between q3 and q1, represents the middle 50% of the observations in a sample

63
Q

define sample variance

A

the average squared distances away the observations in a sample are from the mean

64
Q

define standard deviation

A

the average distance away the observations in the sample are from the mean

65
Q

what would the z score be of an observation one standard deviation above or below the mean?

A

above = 1, below = -1

66
Q

value of interval between mean - standard deviation < x < mean plus one standard deviation

A

66% of observations are within this interval

67
Q

value of interval between mean - 2 standard deviations < x < mean plus two standard deviations

A

75% of observations are within this interval

68
Q

value of interval between mean - 3 standard deviations < x < mean plus 3 standard deviations

A

99% of observations are within this interval

69
Q

define outlier

A

an unusually large or small value in the sample

70
Q

3 possible sources of outliers

A

measurement error, data entry error, observations from a different population have been included

71
Q

what does CS stand for?

A

pearson coefficient of skewness

72
Q

when cs is larger than 1, what does this mean?

A

distribution is significantly skewed to the right

73
Q

when cs is less than -1, what does this mean?

A

distribution is significantly skewed to the left

74
Q

when cs is between or equal to -1 and 1, what does this mean?

A

the distribution is symmetrical and there is no significant skew

75
Q

midpoint for grouped data

A

middle of interval

76
Q

what does adding frequencies for grouped data tell us?

A

the sample size

77
Q

how to find grouped median

A

can be approximated by the midpoint of the interval in which the median would fall

78
Q

how to find modal class (mode for grouped data)

A

not possible to estimate mode, but can state interval with highest frequency of observations

79
Q

how to find range for grouped data

A

difference between first interval and last interval ignoring equal to signs

80
Q

population: μ, sample:

A

x bar

81
Q

population: σ, sample:

A

s

82
Q

population: σ^, sample:

A

s^

83
Q

in order for the inference step to produce good results about the population, what myst be sample be?

A

representative of the population (all aspects and features in the population must be represented in some way)

84
Q

3 properties of a good, representative sample

A

reliable, valid, unbiased

85
Q

define a reliable sample

A

repeated samples from the same population give the same conclusion

86
Q

define a valid sample

A

measurements must be determining of the aspect of the population you are interest in, not some other aspect of the population

87
Q

define an unbiased sample

A

sample does not favour any portion of the population over any other portion (estimated mean approaches actual mean as sample increases)

88
Q

define random sample

A

a sample chosen without any preset pattern or scheme - cannot predict if a certain member of the population will be chosen or not

89
Q

6 sampling methods

A

simple random sample, sequential sample, stratified sample, proportional sample, cluster sampling, multi-stage sampling

90
Q

define simple random sample

A

each member of the population has an equal chance to be selected for the sample

91
Q

give an example of simple random sample

A

names in a hat

92
Q

define sequential sample

A

members of the population are ordered in some way, members are chosen at some pre-determined interval

93
Q

give an example of sequential sample

A

assembly line

94
Q

define stratified sampling

A

population is naturally grouped in layers or strata, random sample from each group

95
Q

define proportional sampling

A

each group in sample is proportional to the population

96
Q

define cluster sampling

A

population is divided into clusters, sample is taken from each cluster

97
Q

define multi-stage sampling

A

population is clustered, random sample chosen from each cluster, random sample then chosen from that sample

98
Q

what 2 sampling methods do not result in a representative sample?

A

self-directed sample, convencience sample

99
Q

define self-directed sample

A

members of the population can choose to be part of the sample of not

100
Q

2 examples of self-directed sample

A

ad, questionnaire

101
Q

define convenience sample

A

use the part of the population that is easily at hand

Data Management (1 decks)

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