PSYC 203 Lecture Notes - Lecture 3: Null Hypothesis, Effect Size, Sample Size Determination
22 Apr 2016
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Uses data from two separate groups to evaluate the mean difference between two groups: example: experimental and control group (placebo & medication, also referred to as between subjects t-tests. Know the steps for executing a t-test and making a decision. Need critical value, obtained value, degrees of freedom t t-table. Critical value: find degrees of freedom, then find the corresponding t-value on t-table (that corresponds to a p of . 05), this t-value is the critical value. Obtain value: answer you get from actual t-test. If obtained value is bigger than the critical value, we reject the null. If obtained value is smaller than the critical value, we fail to reject the null. Degrees of freedom for independent t: (n1 -1) + (n2 -1) Definition: number of scores in the final calculation of a statistic that are free to vary: example: a sample of 3 scores has a mean of 5.
