# Stats Chapter 2

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1. Frequency Distribution
• A table
• that shows classes or intervals of data with a count of the number of
• entries in each class.
• The frequency, f, of a
• class is the number of data entries in the class.
2. Midpoint of a class
Lower class limit + Upper class limit divided by 2
3. Class boundaries
• The
• numbers that separate classes without forming gaps between them..
• The
• distance from the upper limit of the first class to the lower limit of the
• second class is 19 – 18 = 1.
• Half
• this distance is 0.5.
4. Relative Frequency Histogram
• Has the
• same shape and the same horizontal scale as the corresponding frequency
• histogram.
• The
• vertical scale measures the relative frequencies, not
• frequencies.
5. Measure of central tendency
• A value
• that represents a typical, or central, entry of a data set.
• Most
• common measures of central tendency:
• §Mean
• §Median
• §Mode
6. Mean (average)
• The sum of all the data
• entries divided by the number of entries.
• Sigma
• notation: Σx = add all of the data
• entries (x) in the data set.
• Population mean: u=Ex/N
• Sample mean:x=Ex/n
7. Median
• The value that lies in the
• middle of the data when the data set is ordered.
• Measures the center of an
• ordered data set by dividing it into two equal parts.
• If the data set has an
• §odd number
• of entries: median is the middle data entry.
• §even
• number of entries: median is the mean of the two middle data entries.
8. Mode
• The data entry that occurs
• with the greatest frequency.
• If no entry is repeated the
• data set has no mode.
• If two entries occur with
• the same greatest frequency, each entry is a mode (bimodal).
9. Range
• The
• difference between the maximum and minimum data entries in the set.
• The data
• must be quantitative.
• Range =
• (Max. data entry) – (Min. data entry)
10. Deviation
• The
• difference between the data entry, x, and the mean of the data set.
• Population
• data set:
• §Deviation
• of x = xμ
• Sample
• data set:
• §Deviation
• of x = xx
11. Fractiles
• are numbers that partition (divide) an
• ordered data set into equal parts.
12. Quartiles
• approximately divide an ordered data
• set into four equal parts.
13. Interquartile Range (IQR)
• The
• difference between the third and first quartiles.
• IQR = Q3Q1
14. Standard Score (z-score)
• Represents
• the number of standard deviations a given value x falls from the mean μ.
15. arithmetic mean
• The arithmetic mean of a
• variable is computed by determining the sum of all the values of the variable
• in the data set divided by the number of observations.
16. population arithmetic mean
• The population arithmetic mean is
• computed using all the individuals in a
• population.
• The population mean is a parameter.
• The population arithmetic mean is denoted by u .
17. sample arithmetic mean
• The sample arithmetic mean is
• computed using sample data.
• The sample mean is a statistic.
• The sample arithmetic mean is denoted by x.
18. the
population mean, µ, is
u = x1 + x2 + xn/N
19. the sample mean, x , is
x = x1 + x2 + xn/n
20. resistant
• A numerical summary of data is said to be resistant if extreme values (very large or small) relative to the
• data do not affect its value substantially.
21. sample variance
• The sample variance is
• computed by determining the sum of squared deviations about the sample mean and
• then dividing this result by n – 1.

## Card Set Information

 Author: SusanneS28 ID: 127791 Filename: Stats Chapter 2 Updated: 2012-01-15 15:33:51 Tags: Stats Chapter Folders: Description: Stats Chapter 2 Show Answers:

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