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Stats > Reading Quiz 1 > Flashcards

Reading Quiz 1 Flashcards

1
Q

Distribution

A

Distribution of a variable indicates what values a variable takes n and the frequency at which it takes on these values

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2
Q

Key features of a histogram

A

Center, spread, shape, outliers

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3
Q

Three basic shapes

A

Symmetric, skewed right, skewed left

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4
Q

Shape of distribution can also be described

A

By referring to number of modes

Uniondale, bimodal, multimodal, or uniform

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5
Q

Measures of center

A

Mean and median

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6
Q

Sample mean

A

Arithmetic average or arithmetic mean, average of a set of data values

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7
Q

Median

A

Middle number

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8
Q

Median position formula

A

Indicates where the median will lie
(n+1)/2
n = number of numbers in the data set
Formula only indicates where median is not what median is

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9
Q

Perfectly symmetric vs skewed

A

If perfectly symmetric, mean equals median

If skewed, mean farther out in long tail than median

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10
Q

Measures of spread

A

Range, interquartile range, five number summary, variance and sample standard deviation

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11
Q

Range

A

Largest number minus smallest number

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12
Q

Interquartile range

A

Q3 - Q1

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13
Q

Five number summary

A

Minimum, Q1, median, Q3, maximum

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14
Q

Most commonly used measure of spread

A

Standard deviation

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15
Q

Variance

A

s^2 = (Σ(x1 - xbar)^2)/(n-1)

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16
Q

Standard deviation

A

The square root of the variance, represented by s
Measures how the numbers are spread out from the mean
s = square root of variance formula
Nonresistant

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17
Q

Deviation of xi from the mean

A

xi - xbar

Sum of all deviations of the mean equals zero

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18
Q

Degrees of freedom

A

Quantity n - 1

Appears in the denominator of the formulas for variance and standard deviation

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19
Q

Symmetric measures

A

Mean and standard deviation

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20
Q

Skewed sets measures

A

Median and five number summary

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21
Q

Outlier

A

An individual observation that falls outside the overall pattern of the graph
striking deviations

22
Q

Outlier test

A

Data point is outlier if it lies more than 1.5 interquartile ranges below Q1 or above Q3

23
Q

two types of graphs most appropriate for categorical data

A

pie charts and bar graphs

24
Q

graph inappropriate for when several percentages don’t represent portions of same whole

A

pie chart

25
Q

want raw data values, center, shape, spread, too many for dot plot, what graph

A

stemplot

26
Q

histogram

A 
breaks the range of values of a variable into classes and displays only the count or percent of the observations that fall into each class
most common graph of distribution of quantitative variable
27
Q

ogive

A

relative cumulative frequency graph
horizontal axis: values of variable
vertical axis: relative cumulative frequency

28
Q

how to find center of ogive

A

horizontal line from 50% on vertical axis to graph, that value is the center

29
Q

time plot axes

A

time is on horizontal axis

30
Q

trend

A

on time plot, overall upward or downward slope

31
Q

seasonal variation

A

time plot, shorter-term, regularly occurring, rise and fall variations

32
Q

resistant measure

A

measure of center of spread is relatively unaffected by extreme observations

33
Q

two resistant measures

A

median and interquartile range

34
Q

first quartile

A

the median of the subset of observations whose position in the ordered list is to the left of the overall median

35
Q

graph that gives picture of five number summary

A

boxplot

36
Q

IQR

A

Q3-Q1

37
Q

difference between regular and modified boxplot

A

regular is graph of five number summary

modified plots suspected outliers individually

38
Q

measures of spread

A

standard deviation and IQR

39
Q

when is standard deviation 0

A

when there is no spread aka all observations are the same value

40
Q

adding same number to each distribution

A

adds a to measures of center and to quartiles but does not change measures of spread

41
Q

multiply each observation by same number

A

multiplies both measures of center (mean and median) and measures of spread (IQR and standard deviation) by b

42
Q

three graphical measures of comparing distributions

A

bar charts, back to back stemplots, and side by side boxplots

43
Q

categorical variables

A

place individuals into groups or categories (qualitative)

44
Q

quantitative variables

A

numeric measures, makes sense to perform arithmetic operations such as adding or averaging

45
Q

most appropriate displays of categorical data

A

pie charts dot plots bar graphs

46
Q

best displays for quantitative data

A

dot plots stem plots histograms

47
Q

bins

A

values in piles, histograms, need to be physically and numerically equal in width

48
Q

rule of thumb bin number

A

square root of number of observations

49
Q

spread

A

level of variability, range also a measure of this

50
Q

standard deviation

A

measure of average distance of all observations from the mean

51
Q

box plots

A

not ideal indicators of shape and should not be used if there are other options

Stats (15 decks)

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