Statistics Ch. 2

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Statistics Ch. 2
2012-09-19 17:51:39
frequency table bar chart data pie distribution relative histogram

Statistics 101 on tables, charts, and graphs
Show Answers:

  1. What is a frequency table?
    • A grouping of qualitative data into mutually exclusive classes showing the number
    • of observations in each class.
  2. 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 theheights of the bars.
  3. What is a Pie Chart?
    A chart that shows the proportion or percent that each class represents of the total number of frequencies.
  4. What is a Frequency Disribution?
    A grouping of data into mutually exclusive classes showing the number of observations in each class.
  5. Relative Class Frequency
    • -Class frequencies can be converted to relative class frequencies to show the fraction of the total number
    • of observations in each class.

    -A relative frequency captures the relationship between a class total and the total number of observations.
  6. 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.

  7. 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.
  8. How to determine the class interval orwidth.
    • 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
  9. 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.