Chapter 3: Frequency Distributions Flashcards Preview

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Flashcards in Chapter 3: Frequency Distributions Deck (21):
0

Frequency Distributions?

listing of score values and their frequency of occurrence..
listed low to high
symbol = f

1

Frequency Distribution of group scores?

listing of scores into class intervals..

2

Steps to making a frequency Distribution?

find range
decide class interval width (i)
list the limits of each class interval
tally raw scores
add up tallies for interval frequency

3

Range =?

highest score - lowest score...

4

Formula for class interval width? (i)

i= range/ number of class intervals

5

Limits of each class interval...the lowest limit must be evenly divisible by....?

i

6

Relative Frequency?
formul?

proportion of total number of scores that occur in each interval..
Relative f = f/N will = 1

7

Cumulative Frequency?
formula?

number of scores that fall below the URL of each interval..
ex: looking at x3?
cum f = x3+x4+x5.......XN

8

Cumulative Percentage?

percentage of scores that fall below URL of each interval...
Cum%= (cumf/n)100

9

Percentile Point??
Formula??
P75?

value on a measurement scale below which a specified % of scores in the distribution fall....
Fn/Fi= DD/i
Fn= frequencies needed
Fi= frequency of interval
DD= desired distance
i= interval width
P75= value below which 75% points fall

10

P50....

P50 = N(.5)

Lower cumf-------------Fi---------------upper cum f

FN= N(.5)- lower cumf
LRL--------------------------?---------------------URL

------------------------i------------------------------
solve for DD...
Percentile point = LRL + DD

11

Percentile Rank?

percentage of scores with values lower than the score in question?
Percentages of scores that fall below a specific raw score..

% rank= (Cum Fl + Fn/n)100


12

Percentile rank of score 55

Lower cumf---------------------fi----------- upper cumf
--------DD------
LRL-------------------55--------------------URL
--------------------i---------------------
solve for Fn
than solve

13

Graphs allow?

allow you to see certain characteristics of your data...you cannot simply see by looking at data..

14

Properties of a graph?
x, y

x axis: data values (horizontal or abscissa)
y= frequency (vertical or ordinate )
y axis should be about 75 percent shorter than the x

15

Bar Graph?

used for nominal or ordinal data.....
bars= freq per category ....
spaces in between them...

16

Histograph?

interval or ratio data...
bars= class intervals.........starting at LRL and URL...point marked is the Midpoint.... URL-LRL....divided by two...LRL + numb..
intervals are continuous
no spaces... very common graph

17

Frequency Polygon?

interval or ratio data
point at each class interval midpoint is calculated not LRL and URL..
meets x axis below and above class intervals..
no diff between histogram and this...

18

Cumulative % curve

interval or ratio data
plot the URL of each class interval (x axis)
y-axis = cum %
visually see percentile points and ranks..

19

Shapes of Frequency Curves..?

Bell curve: normal distribution.....most in the middle...less on lower and upper extremes..
Rectangular or Uniform Distribution: worst one...data is all kind of the same...avg...
U-shaped distribition (or inverted): can have two normal distributions if extended... High concentration on either side...middle is lower..
above are all SYMMETRICAL..
Negative skewed ... to the right..extremes..
positive skewed:......to the left...extremes..
(layed down p)
J curve: Very extreme.... on one side...

20

Exploratory Data Analysis?
Stem and Leaf?

useful for small data sets... x<100
keeps all original data..
most common
alt to histogram...
5 I 8
stem leaf