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pol 51 lecture 10

# pol 51 lecture 10 - statistic Has standard deviation get...

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Measurement metric (know what that means for midterm) If you ignore Z you can get completely wrong inferences. Difference of means test (continuous X, categorical Y). statistically significant (measurably different from 0). Frequently used test when analyzing experimental data because this is a BIVARIATE TEST and experiments is the only time when you don’t need to worry about Z. Difference of means test: we have two groups/samples of data and we want to know if the means are the same. We should also wonder if they have the same variance, standard deviation, mode, ect. Mean is most common because a lot of phenomenon has normal distribution and that focuses mostly on the mean. We do it because IT IS CONVENIENT. Suppose the null hypothesis is true, then how unlikely is the data? X^2 bigger than critical value, significant; smaller than critical value, not significant T test measures the difference of means. The further apart the means are, the bigger the t

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Unformatted text preview: statistic. Has standard deviation get larger, then standard error gets larger, confident intervals get larger, but t statistic gets smaller. So we have a statistic and now we need to compare it to a critical value. If statistic is greater than critical value, then there is relationship between two variables’ if the statistic is less than crictial value, then no relationship. First we need to know degrees of freedom. This gets you through hurdle 3 Correlation: Positive correlation – as X increases, Y increases Negative correlation – as X decreases, Y decreases Use Pearson’s R If all points on line and positive, then it equals 1. If all the points on line and negative slope, then it equals -1. Are sure are we that the correlation is either positive or negative? First get the t statistic and see if it’s greater than or less than critical value. So now we have to see if it’s substantly significant....
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pol 51 lecture 10 - statistic Has standard deviation get...

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