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freq dist

# freq dist - Quantitative Methods Chapter 2 Frequency...

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© John M. Ackroff 2008 Quantitative Methods Chapter 2: Frequency Distributions and Histograms http://www.rci.rutgers.edu/~ackroff/Q January 29, 2008

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© John M. Ackroff 2008 A word about CPEs… CPEs are due at the beginning of class. Staple each set together, and keep a copy for yourself. If lecture has begun when you arrive, you may turn in your CPEs late. You will receive credit for at most 2 or 3 late CPEs. If you have some situation that causes you to be late routinely, provide documentation to your instructor and we will make special
© John M. Ackroff 2008 Last time We talked about N, μ, σ 2 , and σ. We learned how to compute them. We talked about frequency distributions in general, but not in any great detail. Tonight we’ll learn more about them.

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© John M. Ackroff 2008 Types of Frequency Distributions Theoretical and Actual Frequency Distributions The theoretical frequency distribution for 100 tosses of a fair coin is 50 heads and 50 tails. The actual frequency distribution for 100 tosses of a fair coin might, and likely would, not be 50 heads and 50 tails. It would probably be close, though.
© John M. Ackroff 2008 Some definitions A frequency distribution is a tabular display of the way scores are distributed across all possible values of a variable. A cumulative frequency distribution makes information more readily available by showing the number of scores at or below each possible score.

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© John M. Ackroff 2008 More types of Frequency Distributions A relative frequency distribution shows the proportion of scores for any value of the variable. RF v = F v /N A relative cumulative frequency distribution shows the proportion of scores at or below any value of the variable. RCF = Σ(F 1 , F 2 , … F v )/N
© John M. Ackroff 2008 Table 2.4 Scores on an exam. What proportion of scores was 4 or lower? (F 0 + F 1 + F 2 + F 3 + F 4 ) / N How many scored X? F X How many did not score X? (N – F X ) (subtraction method)

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Table 2.4, cont’d What proportion of the students scored X? F
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freq dist - Quantitative Methods Chapter 2 Frequency...

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