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stat101 > skills test 1 > Flashcards

skills test 1 Flashcards

1
Q

define descriptive statistics

A

those with a purpose to describe data by summarising, graphing etc.

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2
Q

define inferential statistics

A

making decisions, estimates or predictions about a larger set of data through hypothesis testing

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3
Q

define a population

A

a set of items/units of interest

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4
Q

define a sample

A

a subcollection of members from a population

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5
Q

define a parameter

A

summary measure about a population

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6
Q

define a statistic

A

summary measure taken from a sample

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7
Q

define a variable

A

measurable characteristic that could change

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8
Q

define a representative sample

A

typical of population and chosen randomly

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9
Q

parameters measure ____ and statistics measure ____

A

populations, samples

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10
Q

define qualitative data

A

something classified into groups or categories

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11
Q

what are the two types of qualitative data

A

nominal and ordinal

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12
Q

what is qualitative nominal data

A

the name of something

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13
Q

what is qualitative ordinal data

A

where the order of the names means something to us

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14
Q

what is quantitative data

A

measured on a numerical scale and maths can be done with the numbers

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15
Q

what are the subcategories of quantitative data

A

interval/ratio

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16
Q

define the mode

A

the value that occurs most often

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17
Q

define the median

A

this is the middle value in ordered sequence

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18
Q

define the mean

A

the average of all the values

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19
Q

what is a left skew

A

a negative skew where the mode is bigger than the median which is bigger than the mean - tail to the left

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20
Q

what is a symmetric shape

A

the mean is the same as the median and mode

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21
Q

what is a right skew shape

A

the mean is bigger than the median which is bigger than the mode - tail to the right

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22
Q

what is spread

A

when the graph is wide there is lots of spread but when the graph is narrow there is little spread as it is very clustered together

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23
Q

what is range

A

maximum minus minimum

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24
Q

what is a deviation

A

the difference between an observation and the mean

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25
Q

how do you find variation

A

find the mean, find the deviations by taking each value and subtracting the mean from it, square each deviation, sum the squared deviations, divide by n-1

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26
Q

how do you find standard deviation

A

square root the variance result from the formula

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27
Q

variance is the ____ of standard deviation

A

square

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28
Q

sample statistics use ____ but population parameters use ____

A

ordinary variable letters, greek letters

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29
Q

what is discrete data

A

a countable number

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30
Q

what is continuous data

A

no gaps between the numbers

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31
Q

what is a bar chart

A

gaps between bars - two types of qualitative data can go on the same graph

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32
Q

what is a pie chart

A

sometimes the pieces can be too small to tell the difference

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33
Q

what is a stem and leaf plot

A

put the first number on the left and the second numbers in sequence on the right - this can show shape, but you wouldn’t do it for a huge number set as it gets way too big

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34
Q

where there are two quantitative variables what graph would you use

A

scatter plot

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35
Q

what is the interquartile range

A

Q3 - Q1

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36
Q

what are quartiles

A

split the data up into 25% chunks

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37
Q

what is the 5 number summary

A

shows the smallest value, lower quartile, median, upper quartile and largest value

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38
Q

if you were asked to show the numbers from a 5 number summary would they be in square or round brackets

A

round

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39
Q

what is an outlier

A

an unusually small or large value - more than 3 standard deviations from the mean or beyond 1.5 x IQR from the ends of the box

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40
Q

how do you make a modified box plot

A

1.5 x IQR, draw fences this amount outside the box. Pull back the fence to the closest value to it to be the ends. Dot any values outside of this

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41
Q

what does a simple price index do?

A

compares the price of an item in one period with another period

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42
Q

what is the formula for price relative

A

Pn/Po

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43
Q

what is the composite price index

A

(total price of a basket of goods in the current period)/(the price of the same basket of goods in the base period)

44
Q

how do you calculate the simple price index

A

price relative x 100, if the result is more than 100 there is a price increase

45
Q

laspeyres index uses _______ products and quantity as the base period

A

the same

46
Q

what is the consumer price index

A

cost of living index that measures the change in the cost of the basket, if the index number is above 1000 the price is increasing

47
Q

how do you find out a price from a certain period using the cpi

A

take the current price and multiply it by (the index for the period we want)/(index for the period where that price came from)

48
Q

what are some drawbacks to the cpi

A

sampling error, time, quality is difficult to measure, introduction of new products not recognised often

49
Q

what is the inflation rate defined as

A

the rate of change between the CPI price level today and the CPI price level one year ago

50
Q

what is on what axis in a time series graph

A

time on the horizontal axis and the same data is measured over and over again on the vertical axis

51
Q

what is a trend in time series data

A

a continuous long term movement

52
Q

what is seasonality in time series data

A

movements in the time series occurring regularly during any period a year or less

53
Q

describe the normal curve

A

symmetric about the mean, median and mode, bell shaped, asymptotic to the horizontal axis

54
Q

what percentage will lie within 1 standard deviation of the mean according to the empirical rule

A

68%

55
Q

what percentage will lie within 2 standard deviations of the mean according to the empirical rule

A

95%

56
Q

what percentage will lie within 3 standard deviations of the mean according to the empirical rule

A

99.7%

57
Q

how do you calculate a z score

A

(observed value - mean)/standard deviation

58
Q

what is a deterministic model

A

one thing determines the other and its an exact relationship - y = B0 + B1x

59
Q

what is a probabilistic model

A

there is a deterministic part but also a random error part due to unpredictability. y = B0 + B1xi + Ei

60
Q

the linear regression model uses what type of graph

A

scatterplot

61
Q

what variable is predictor in a linear regression

A

x axis

62
Q

what variable is the response in a linear regression

A

y axis

63
Q

whats the difference between interpolation and extrapolation

A

interpolation - using the linear regression model for values where the model was designed for that part of the data

extrapolation - using the model for a value it wasn’t designed for, which can be risky

64
Q

when you do linear regression analysis in excel, how do you find the equation of the line

A

“intercept” is B0 or the y intercept, “X variable” is B1 or the gradient

65
Q

what is a standard form for interpreting a y intercept

A

“____ (y variable) is 730385 units when ____ (x variable) is zero”

66
Q

what is a standard form for interpreting a slope (B1)

A

____ (y var) is expected to _____(increase/decrease) by _____ (amount of gradient) for ______ (each increase, each extra, one extra - of the x variable)

67
Q

how do we tell how good the model is

A

coefficient of determination - R square - convert to a percentage - the closer to 100% the better the model is / “99% of the variation in y can be explained by the variation in x”

68
Q

what is the difference between regression and correlation

A

regression uses one explanatory variable to predict another response variable, correlation treats both variables symmetrically and it doesn’t matter what is on what axis because it is not a measure of causality

69
Q

what does correlation measure

A

the strength and direction of the linear relationship between x and y

70
Q

if there is no linear relationship, the correlation coefficient will be?

A

0

71
Q

a perfectly positive correlation relationship will be?

A

1

72
Q

a perfectly negative correlation relationship will be?

A

-1

73
Q

what is the coefficient of correlation called in excel

A

multiple R

74
Q

what is an observational study

A

measuring and observing specific characteristics but not seeking to modify the subjects being studied

75
Q

what is an experiment

A

we apply some treatment and then observe the effect on the subjects - there is someone driving the experiment

76
Q

what types of sampling are there

A

simple random sampling, random, stratified, cluster, systematic, convenience, snowballing

77
Q

what is simple random sampling

A

every possible sample of the same size n has the same chance of being chosen

78
Q

what is a random sample

A

all members of the population have the same chance of being chosen

79
Q

what is stratified random sampling

A

the population is divided into groups called strata. a random sample is drawn from each strata. add these samples from each strata together to get a full sample

80
Q

what is cluster sampling

A

divide population into groups called clusters. randomly choose some of the clusters and sample all members

81
Q

what is systematic sampling

A

select some starting point and then measure every ‘n’th value after that

82
Q

what is convenience sampling

A

choose whoever is easy to include such as people walking by

83
Q

what is snowball sampling

A

survey subjects are selected based on referal from other respondents

84
Q

what type of samples are probabilistic (can be applied to the underlying population)

A

simple random, stratified, cluster, systematic

85
Q

what types of bias are there

A

selection, interviewer, question

86
Q

can the population parameter and the sample statistic be the same

A

no even with no bias they will be different because no two samples are the same - this is called a sampling error

87
Q

what are examples of non-sampling errors

A

selection problems, non-response bias, measurement error

88
Q

define probability

A

the likelihood of an event

89
Q

probabilities lie between ______

A

0 and 1 and cannot be negative or more than 1

90
Q

define an event

A

any collections of results or outcomes of a procedure

91
Q

define a simple event

A

an outcome that cannot be further broken down into simpler components

92
Q

define a sample space

A

these consist of all possible simple events

93
Q

how do we write “the probability of a”

A

pr(A)

94
Q

a or b means?

A

all outcomes in a and b or both

95
Q

a and b means?

A

only the overlap of the two circles as a and b must occur together

96
Q

what are odds

A

probabilities but written as a ratio of the probability that the event does occur to the probability the event doesn’t occur

97
Q

what are probabilities from equally likely events

A

number of ways the outcome can happen / number of total outcomes

98
Q

what are relative frequency probabilities

A

estimating a frequency with which the event occurs based on historical data

99
Q

what are subjective probabilities

A

someones guess at how likely some event is

100
Q

what is the additive rule

A

pr(a or b) = pr(a) + pr(b) - pr(a and b)

101
Q

what are collectively exhaustive events

A

at least one of the events must occur

102
Q

what are mutually exclusive events

A

the two events cannot occur at the same time

103
Q

what is a conditional probability

A

the probability that event a occurs given that event b has already occured

104
Q

what are statistically independent events

A

when events are independent, one event occurring doesn’t influence the probability of another event

105
Q

what does the multiplicative rule prove and what is it

A

pr (a and b) = pr (a) x pr (b)

if this is true, the events are independent

106
Q

how do you find the probability from a tree diagram

A

multiply along the branch

107
Q

what does a line ontop of a letter mean

A

the event does not occur

stat101 (3 decks)

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