Chapt.%206

Essentials of Statistics for the Behavioral Science

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    Chapter 6 Probability
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    Introduction A statement of probability is an assertion about how  likely it is that a particular event or relation will  occur.        Levels of probability are expressed in terms of  numbers that range from .00 to 1.00.      .00 means that thing will Not occur and 1.00 means that it is certain to occur.
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    Introduction Probability is the basis for all inferential statistics.       Probability tells us how likely our experimental  results are due to chance.       We introduce chance into behavioral research by  using samples in our studies.       We can’t eliminate uncertainty - but we can  measure it. 
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    Some Probability Basics Probability is typically expressed as a proportion.       The probability of an event A (written p(A)) equals  the number of outcomes defined as A divided by  the number of all possible outcomes (i.e.,  A,B,C,D,E, etc).      Number of A outcomes Number of All outcomes 
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    Some Probability Basics Probability and random sampling.             The accuracy of probability estimates is  dependent upon random sampling.      Random sampling must meet two basic  requirements. 1. Each outcome has an equal probability of  being selected.  2. Probability must be constant for each  individual event. 
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    Probability and frequency distributions   Probability is essentially identical to our concept of  relative frequency. Example      Construct a frequency distribution from a deck of  cards (ignoring suits).   Relative frequency and probability are both  calculated by dividing the number of individual  outcomes from number of all outcomes.
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  Probability and frequency distributions In inferential statistics, we find probabilities from  frequency distributions that represent relative  frequencies graphically.       These are frequency polygons.       Frequency polygons have a perimeter.      Frequency polygons have an area.
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Chapt.%206 - Chapter 6 Probability Introduction

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