STAT 1400 Lecture Notes - Lecture 5: Confidence Interval
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Don"t forget to go to office hours for help!! Workbook 6-3: answer: (111. 2, 118. 6) mmhg, answer: the sample needs to be randomly selected, and bp needs to be normally distributed. To estimate the difference between the means of two independent groups (m1 m2), we use the difference between both sample averages y - Seeds are randomly assigned to be planted in pots with soil treated with pesticide or in pots with untreated soil. Seedling growth (in mm) is recorded after 2 weeks. A 95% confidence interval for ( 1 - 2) is: y. The two-sample statistic is most robust when both sample sizes are equal and both sample distributions are similar. But even when we deviate from this, two-sample tests tend to remain quite robust. As a guideline, a combined sample size (n1 + n2) of 40 or more is sufficient to work even with the most skewed distributions.
