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Unformatted text preview: Example : A random sample of 400 individuals who filed a tax return between April 10 and April 15 (the last five days to file returns) had a sample mean refund of $910 with a sample standard deviation of $1600. What is a 95% confidence interval for the average refund for those who file returns in the last 5 days? Now : Individuals who file taxes before the last 5 days (prior to April 10) have an average refund of $1056. A researcher suggests that the reason indi viduals wait until the last five days is that on average these individuals receive lower refunds than do early filers. Does the data support this hypothesis? To answer questions like this we will use a statistical inferential technique called hypothesis testing . 1 Hypothesis Tests We want to determine whether a statement about the value of the pop ulation parameter should or should not be rejected. We first make a tentative assumption about the population called the null hypothesis, denoted by H . We define another hypothesis called the alternative hypothesis, denoted by H a , that is the opposite of the null hypothesis....
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This note was uploaded on 01/24/2011 for the course STATISTICS 19897 taught by Professor Jager,abigaill during the Fall '10 term at Kansas State University.
 Fall '10
 Jager,AbigailL
 Standard Deviation

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