Statistics I -chapter 2
Why should the number of classes in a frequency distribution be between 5 and 20?
In order to detect any patterns
Ogive
Is a cumulative frequency graph that displays cumulative frequencies
Integer Data- class limits and boundaries differ by
0.5
Find class width for min=10, max=96, 6 classes....and lower and upper class limits
96-10=86....(range)....divide by 6 and round up =15... Lower class limits 10,25,40,55,70,85. Upper class limits 24,39,54,69,84,99
After constructing a relative frequency distribution summarizing IQ scores of college students, what should be the sum of the relative frequencies?
If percentages are used, the sum should be 100%. If proportions are used, the sum should be 1.
Class limits
Least and greatest numbers that can belong to a class
Range
Minimum subtracted from maximum
Upper limit for first class is
One less than the lower limit of second class
What are some benefits of representing DATA SETS using frequency distributions?
Organizing the data into a frequency distribution can make patterns within the data more evident.
To find class's upper limits, find first class then add min number to each.....example- min=9, max=69, 7 classes....lower limits for first class is 9, second is 18 (9+9)....upper limit is 18-1=17....
Other classes (add 9) is 17, 26, 35, 44, 53, 62, 71
To find class width
Subtract minimum from maximum and divide by number of classes...(round to nearest whole number).
To find lower limits of all classes (min=9, max=69, 7 classes).....
Take first min, which is 9 then add 9 to each class for all 7 classes.....answer is 9,18,27,36,45,54,63
Relative Frequency of a class
is the percentage of the data that falls in that class
Class width
is the range (max.-min.) divided by number of classes.....round up to nearest whole number
The difference between the maximum and minimum data entries is called the
range
The class width is
the distance between lower (or upper) limits of consecutive classes.
The midpoint of a class is
the sum of its lower and upper limits divided by two
In a Frequency distribution,
class width is the distance between the lower and upper limits of consecutive classes.
frequency polygon
displays class frequencies
Each class has an upper class limit, which
Is the greatest number that can belong to the class.
Each class has a lower class limit, which
Is the least number that can belong to the class.
Cumulative frequency of a class
Is the sum of the frequencies of that class and all previous classes
What are some benefits of using GRAPHS of frequency distributions?
It can be easier to identify patterns of a data set by looking at a graph of the frequency distribution.
Class Boundaries
are the numbers that separate classes without forming gaps between them; they ensure that consecutive bars of a histogram touch.