STAT 2510 Lecture 4: Stats 2510 Lec. 4
25 Jan 2017
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Document Summary
Two types of descriptive measures: measures of center looking at different ways to describe what a typical value is of data set, measures of variation spread of the data. Mean of data set sum of observations divided by number of observations (average) Median middle value when arranged in smallest to largest: position is n+1/2, n=number of observations (sample size, odd number of observations=will be exactly in middle, even number=mean/average of middle two values. Mode values that appear the most frequently: need frequency distribution, possible to have no mode or multiple modes. The mean is sensitive to extreme observations, but the median is not. Right skew (cid:373)ea(cid:374) is greater tha(cid:374) (cid:373)edia(cid:374) (cid:271)e(cid:272)ause it"s pulled i(cid:374) dire(cid:272)tio(cid:374) of skew. Mean is pulled in the direction of a skew. Xi x sub i ; denoting it observations. For variable x ,the standard deviation of the observations for a sample is called ssd. Denoted by sx or when no confusion will arise simply s.
