Psyc 60 Hypothesis Testing

Psyc 60 Hypothesis Testing - Hypothesis Testing An example....

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    Hypothesis Testing
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    An example… Suppose that we want to compare the  crime rate in San Diego with the crime  rate in the rest of the country. Is there more or less crime in San Diego  than the national average?
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    An example… First, we start with the hypothesis that the  crime rate on average in San Diego is the  same as the national average. To test our hypothesis, we ask what  sample means would occur if many  samples of the same size were drawn at  random from our population  if our  hypothesis is true .
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    An example… We can now refer to the sampling  distribution of the mean, for an infinite  series of samples of size  n , drawn from a  population whose mean is the same as the  national average, and we compare our  sample mean with those in this sampling  distribution. If our hypothesis is true, then the  distribution of sample means will be  centered about the national average.
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    An example… Suppose that the relationship between our  sample mean and those of the sampling  distribution of the mean looks like this… value. Our hypothesized  value.
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    An example… If so, our sample mean is one that could  reasonably occur if the hypothesis is true,  and we will retain our hypothesis as one  that could be true.  (The crime rate of San  Diego is the same as the national  average.)
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    An example… On the other hand, if the relationship  between our sample mean and those of  the sampling distribution of the mean looks  like this…
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    An example… Our sample mean is so deviant that it  would be quite unusual to obtain such a  value when our hypothesis is true.  In this  case, we would reject our hypothesis and  conclude that it is more likely that the crime  rate of San Diego is not the same as the  national average. The population represented by the sample  differs significantly from the comparison  population.
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    Null Hypothesis The hypothesis that we put to the test is  called the  null hypothesis , symbolized   H 0 . The null hypothesis usually states the  situation in which there is no difference  (the difference is “null”) between  populations.
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    Alternative Hypothesis The  alternative hypothesis , symbolized   H A , is the opposite of the null  hypothesis. The alternative hypothesis is also  identified as the research hypothesis, or  the “hunch” that the investigator wants  to test.
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    Null and Alternative  Hypotheses Both H 0  and H A  are statements about  population parameters, not sample statistics.
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This note was uploaded on 01/30/2009 for the course PSYC 60 taught by Professor Ard during the Spring '08 term at UCSD.

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Psyc 60 Hypothesis Testing - Hypothesis Testing An example....

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