Transcript PowerPoint (3.1)

Learning Goal:
To be able to create and interpret frequency tables.
Definition
A basic frequency table has two columns
 One column lists all the categories of
data.
 The other column lists the frequency of
each category, which is the number of
data values in the category.
The grades on a statistics
exam were:
AABCCCBBBACCCCDF
FAAFFCCCBBBAACDF
AABCCCDA
Construct a frequency table.
Definitions
 The relative frequency of any category is
the proportion or percentage of the data
values that fall in that category:
Relative frequency=(frequency in category)/(total frequency)
 The cumulative frequency of any
category is the number of data values in
that category and all preceding categories.
 Add relative frequency and cumulative
frequency to the previous frequency table.
Binning Data
 When it is impossible or impractical to have a
category for every value in a data set, we bin (or
group) the data into categories (bins), each covering
a range of possible data values.
 In general, the number of bins should be between 5
and 20. The purpose of binning data is to be able to
understand the distribution of the data.
Copyright © 2009 Pearson Education, Inc.
Frequency table with the data binned.
Copyright © 2009 Pearson Education, Inc.
Dog Sled Racing
How long does it take to finish the 1161-mile Iditarod
Dog Sled Race from Anchorage to Nome, Alaska?
Finish times (to the nearest hour) for 57 dogsled teams
are shown below:
261
271
236
244
279
296
284
299
288 288
247
256
338
360
341
333
261
266
287
296
313 311
307
307
299
303
277
283
304
305
288
290
288 289
297
299
332
330
309
328
307
328
285
291
295 298
306
315
310
318
318
320
333
321
323
324
327
Use bins to construct a frequency table.