AP STATISTICS
LESSON 1 - 1
Shape
Ogives
and
Timeplots
Essential Question:
What shapes can be expected and
how are Ogives and Timeplots
made?

To organize data and recognize basic shapes
that are formed.

To create Ogives (relative cumulative frequency
graphs)

To organize data into Timeplots.
Warm – up #1
Pages 16 - 17
Problem 1.8:
ARE YOU DRIVING A GAS GUZZLER?
Warm – up # 2
Page 24
Problem 1.15
CHEST OUT, SOLDIER!
Symmetric and Skewed
Distributions

A distribution is symmetric if the right and left sides
of the histogram are approximately mirror images
of each other.

A distribution is skewed to the right if the right side
of the histogram ( containing the half of the
observations with larger values) extends much
farther out than the left side. It is skewed to the left
side if the histogram extends much farther out than
the right side.
Symmetry and Skewed
to the Right
Symmetric
Distribution:
The two sides of the
histogram are roughly
the same shape, so we
call the distribution
symmetric.
Skewed Right:
The distribution has a
single peak, but is
skewed to the right.
The right tail of the
histogram extends
out much father than
the left tail.
Note: The vertical
scale is not the
count of words but
the percent of all of
Shakespeare’s
words that have
each length. A
histogram of
percents rather than
counts is convenient
when the counts are
very large or when
we want to compare
several
distributions.
Pages 26 - 27
Problem 1.16:
STOCK RETURNS
Percentile

The pth percentile of a distribution is the
value such that p percent of the
observations fall at or below it.

Relative is a word used in Statistics that
indicates that percents are to be used.
Ogive
(Relative cumulative frequency graph)
An Ogive tells us the relative standing of an individual
observation.

Step 1: Decide on class intervals and make a frequency
table, just as in making a histogram. Add three columns
to your frequency table: relative frequency, cumulative
frequency, and relative cumulative frequency.

Step 2: Label and scale your
aces and title your graph.
 Step 3: Plot a point
corresponding to the relative
cumulative frequency in each
class interval at the left endpoint
of the next class interval.
How to Construct an Ogive
Pages 29 - 30

To get the values of relative frequency column,
divide the count in each class interval by 43.
Multiply by 100 to convert to a percentage.

To fill in the cumulative frequency column, add
the counts in the frequency column that fall in
or below the current class interval.

For the relative cumulative frequency column,
divide the entries in the cumulative frequency
column by total number of individuals.
Ogive Exercise
Page 31
Exercise 1.20
SHOPPING SPREE, II
Time plots

A time plot of a variable plots each observation
against the time a which it was measured.

Always mark the time scale on the horizontal
axis and the variable of interest on the vertical
axis.

If there are not too many points, connecting the
points by lines helps show the pattern of
changes over time.
Time plots
(continued…)
Look for :
Trends – overall pattern
that indicates a longterm upward or
downward movement
over time.
Seasonal variation – a
pattern that repeats
itself at regular time
intervals.