due on 02/22/2016 - STATISTICS- RESEARCH METHOD - GRAPHIC REQUIRED - central tendency and dispersion measures
allisky
chapter_11_part_iii_powerpoint_handout.pdf
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Chapter 11: Part III In this chapter you will learn:
Normal Distribution
Exploratory Data Analysis Techniques
Standard deviation used extensively in inferential statistics; used to estimate how close a sample characteristic is to the corresponding population parameter
Normal distribution uses the standard deviation as a ‘ruler’
Normal Curve characteristics: ◦ Bell-shaped and symmetric ◦ Mode, Median and Mean are equal and located at the
center of the distribution
◦ Fixed proportion of data lie between the mean and any fixed point on the curve
68% of cases fall within 1 standard deviation of
the mean
95% fall within 2 standard deviations
99.7% fall within 3 standard deviations
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Z-scores measure the distance, in standard
deviations, of an observation from the mean
where
z is the z-score
Xi is an observation
is the mean of the distribution
S is the standard deviation of the distribution
S
XX z i
If we know that the mean of a distribution is 100
and the standard deviation is 20, calculate and
interpret the z-score for these numbers:
115
75
75.0 20
100115
z
00.1 20
10080
z
This value is 0.75 standard deviations above the mean.
This value is 1.0 standard deviations below the mean.
Emphasizes becoming familiar with the data,
rather than simply summarizing with one or two
statistics
New measures of center of spread used
◦ Trimmed Mean: Mean is calculated after removing outliers or a % of cases
5% Trimmed Mean: Mean calculated after the bottom and
top 5% of data are removed
◦ Midmean: uses only the middle 50% of data
New data displays: Box Plot, also called Box-and-
Whisker
Minimum, Q1, Median, Q3, Maximum
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Very useful for comparing two or more data sets
Computer software for data management,
analysis discussed
Methods for presentation, analysis reviewed
◦ Frequency distributions
◦ Graphical displays: bar graphs, pie charts, histograms
Various descriptive statistics reviewed
◦ Quantitative measures
◦ Measures of center
◦ Measures of variation
Normal distribution introduced
Exploratory Data Analysis described
