Example 138: When investigating the link between consuming canned foods and bisphenol A (BPA) levels in people, researchers found that 26 subjects who ate a can of soup everyday for five days had average BPA levels of 20.8 micrograms per liter of urine and a standard deviation of 3.1 micrograms per liter. For 27 subjects who ate fresh soup, their mean levels were 1.1 micrograms per liter of urine and a standard deviation of 0.5 micrograms per liter. At the 5% significance level, test the claim that consuming canned soup raises the concentration of BPA in urine (assume BPA levels are normally distributed and do not assume equal variances).

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Example 138

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