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PSY 1110 > Unit 2 > Flashcards

Unit 2 Flashcards

1
Q

∑ means…

A

to sum

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2
Q

∑X means…

A

to add all X values

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3
Q

∑X ^2 means…

A

square each X value, then sum

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4
Q

(∑X)^2 means…

A

add all X values first, then square the sum

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5
Q

∑XY means…

A

multiply each X value by corresponding Y value

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6
Q

(∑X)(∑Y) means…

A

add all X, add all Y, then multiply the two sums

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7
Q

∑(X-Y) means…

A

take the sum of X minus sum of Y

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8
Q

what does “N” mean

A

population size
number of cases/participants in the population

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9
Q

what does “n” mean

A

sample size
number of cases/participants in the sample

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10
Q

what is a Frequency Table

A

a table that organizes the data based on how often scores occur

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11
Q

describe the process of Simple Frequency Distribution

A
  1. go through raw data. find lowest/highest scores
  2. list each possible score between low & high, including them
  3. tally the corresponding frequencies
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12
Q

what is Raw Data

A

data as originally collected
ex: stream of numbers

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13
Q

define “grouped frequency distribution”

A

group the data into “class intervals”

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14
Q

what are “class intervals”

A

groups numerically defined in such a way that any given raw score can belong to one and only one group

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15
Q

what are the steps in making a grouped frequency distribution

A
  1. estimate the number of class intervals between 5 and 20
  2. find the highest and lowest cases, subtract those two for the range
  3. divide the estimated number of class intervals into the range (this determines class interval size)
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16
Q

what is cumulative frequency

A

frequency of all scores at or below a particular score. its a running total of frequencies

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17
Q

what is relative percentage

A

percentage of time the raw score occurs in a sample or population
relative % = (f/n) x 100

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18
Q

what are real limits

A

refers to the points falling one half a measurement unit above and below a particular number

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19
Q

what is cumulative percentage

A

also referred to as “percentile”
percentage of cases at or below a particular score
(the score at the nth percentile is the upper real limit of the class interval or of the score)

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20
Q

what are midpoints

A

the halfway point within the class interval.
the average of upper and lower real limits.
equal to class interval size!!

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21
Q

what does the x-axis represent

A

scores OR midpoints (in grouped freq. distribution)

22
Q

what does the y-axis represent

23
Q

describe a histogram

A
  • interval or ratio data
  • nice graph for discrete variable
  • series of vertical bars centered over the score on x-axis
  • height of bar = frequency
  • adjacent bars touch as long as there is a frequency
24
Q

describe a frequency polygon

A
  • interval or ratio data
  • nice graph for continuous variable
  • series of dots centered over score on x-axis
  • height = frequency
  • connect the dots with straight lines, in order
25
describe a bar graph
- nominal or ordinal data - series of vertical bars centered over score on x-axis - height = frequency - adjacent bars do NOT touch (because they are categories, not numbers)
26
what is modality
the number of meaningful peaks
27
is normal distribution symmetrical?
yes
28
how many peaks does unimodal have
one peak
29
what is a negatively skewed graph
starts low, goes uphill (climbing roller coaster) lot of high, few low
30
what is a positively skewed graph
starts high, goes downhill (descending roller coaster) lot of low, few high
31
describe skewed distributions symmetry
they lack symmetry
32
what is a statistical picture, and what are the components
things to include in a good visual display of statistical information 1. the data should stand out clearly from the background 2. there should be a title and purpose of the picture 3. everything should be clearly labeled (pic segments, axes, start @ zero or not) 4. there should be a source given for the data 5. there should be as little "chart junk" as possible
33
what are the two types of "pictures of categorical data"
pie charts and pictograms
34
describe pie charts
- useful when only one categorical variable is measured - pie charts show what percentage of the whole falls into different categories
35
describe pictograms
like a bar graph, except it uses pictures related to the topic of the graph
36
what are the types of "pictures of measurement variable"
line graph and scatterplot
37
describe line graphs
useful for displaying how a measurement variable changes over time
38
describe scatterplots
- useful for describing the relationship between two measurement variables - each dot on the plot represents one individual
39
define measures of central tendency
a score that summarizes the location of a distribution on a variable
40
what is mean
arithmetic average of all scores in the distribution. interval/ratio best measure of CT when distribution is symmetrical
41
what is median
"Md." can represent ordinal, interval, ratio data. exact midpoint of the distribution. always the score at 50% percentile (best measurement of CT when distribution is skewed)
42
what is mode
"Mo." can represent nominal, ordinal, interval, ratio data. only measure of CT for nominal. most frequently occurring score(s) in data.
43
name the 2 factors that contribute to best measurement of central tendency
1. type of data 2. shape of distribution
44
all 3 measurements are equal at the same point for which type of graph
normal distribution
45
define measures of variability
a score/value that indicates how spread out the scores are in a distribution **measure of the distance of scores (how close/far)
46
define range
measurement of the width of the entire distribution. highest score - lowest score = range
47
define interquartile range
middle 50% of the distribution. arrange scores according to magnitude! score at 75% - score at 25% = IQR
48
define variance
the average of the squared deviations of the scores around the mean (base point)
49
can standard deviation be negative?
no. never.
50
describe normal distribution
- many distribution of measures conform to the normal curve - actually a theoretical distribution based on a population of an infinite # of cases
51
what does a z-score do or tell us
we use z-score if we need to standardize scores or make comparisons. z-score represents the # of standard deviation units. z-score indicates how far away from the mean the observation is

PSY 1110 (2 decks)

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