PSYC 305 Lecture Notes - Lecture 4: Null Hypothesis, Normal Distribution, Simple Random Sample
11 Mar 2013
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Document Summary
T-test: where standard deviation of population is unknown. In- stead, it follows the t-distribution: the t-distribution was discovered by william s. gosset in 1908. Gosset was a statistician employed by the guinness brewing company which had stipulated that he not publish under his own name. He therefore wrote under the pen name student": also called student"s t distribution. The t distribution: varies in shape according to the degrees of freedom (df) = n-1, the t distribution approaches the standard normal distribution as df becomes large, the approximation is quite good for df > 30. Hypothesis testing about a single mean: t-test: calculate the value of t-statistic (or simply t-value) for your sample mean with m and sm. If your t-value in absolute value is larger than the critical value, you may reject the null hypothesis with the significance level of . 05.
