Statitistics Revivew Ch.1-3
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What is a frequency table?
- A grouping of qualitative data into mutually exclusive classes showing the number
- of observations in each class.
What is a Bar Chart?
- A graph in which the classes are reported on the horizontal axis and the class frequencies on the vertical axis. The class frequencies are proportional to the
- heights of the bars.
What is a Pie Chart?
A chart that shows the proportion or percent that each class represents of the total number of frequencies.
What is a Frequency Disribution?
A grouping of data into mutually exclusive classes showing the number of observations in each class.
Relative Class Frequency
-Class frequencies can be converted to relative class frequencies to show the fraction of the total numberof observations in each class.
-A relative frequency captures the relationship between a class total and the total number of observations.
In frequency distribution what is a class interval?
Class interval: The class interval is obtained by subtracting the lower limit of a class from the lower limit of the next class
How to decide on the number of classes for a frequency distiribution.
A useful recipe to determine the number of classes (k)is the “2 to the k rule.” such that 2k > n.
i.e. There were 180 vehicles sold, so n = 180. If we try k =7, then 27 = 128, somewhat less than 180. Hence, 7 is not enough classes. If we let k = 8, then 28 = 256, which is greater than 180. So the recommended number of classes is 8.
How to determine the class interval or
- The formula is: i ≧ (H-L)/k where "i" is the class interval, H is the highest observed value, L is the lowest observed value, and k isthe number of classes.
- Round up to some convenient number, such as a multiple of 10 or 100. Use a class width of $400
How to determine Relative Frequency Distribution.
- To convert a frequency distribution to a relative frequency distribution, each of the class frequencies is divided by the total number of observations.
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