Chapter 3: Frequency Distributions

Question 1

Frequency Distribution of group scores?

Answer 1

listing of scores into class intervals..

Question 2

Steps to making a frequency Distribution?

Answer 2

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

Question 3

Range =?

Answer 3

highest score - lowest score…

Question 4

Formula for class interval width? (i)

Answer 4

i= range/ number of class intervals

Question 5

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

Answer 5

i

Question 6

Relative Frequency?

formul?

Answer 6

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

Question 7

Cumulative Frequency?

formula?

Answer 7

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

Question 8

Cumulative Percentage?

Answer 8

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

Question 9

Percentile Point??
Formula??
P75?

Answer 9

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

Question 10

P50….

Answer 10

P50 = N(.5)

Lower cumf————-Fi—————upper cum f

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

————————i——————————
solve for DD…
Percentile point = LRL + DD

Question 11

Percentile Rank?

Answer 11

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

Question 12

Percentile rank of score 55

Answer 12

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

Question 13

Graphs allow?

Answer 13

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

Question 14

Properties of a graph?

x, y

Answer 14

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

Question 15

Bar Graph?

Answer 15

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

Question 16

Histograph?

Answer 16

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

Question 17

Frequency Polygon?

Answer 17

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...

Question 18

Cumulative % curve

Answer 18

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

Question 19

Shapes of Frequency Curves..?

Answer 19

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…

Question 20

Exploratory Data Analysis?

Stem and Leaf?

Answer 20

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

Question 21

Frequency Distributions?

Answer 21

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