Example 136: When investigating the link between birth weights and IQ scores, researchers found that 28 subjects with birth weights less than 1000g had a mean IQ of 95.5 and a standard deviation of 16.0. For 27 subjects with normal birth weights, the mean IQ was 104.9 with a standard deviation of 14.5. At the 5% significance level, test the claim that low birth weight children have lower IQs than normal birth weight children (assume IQ scores are normally distributed and the variances are equal). Is there a possible problem with the assumption of equal variances here?

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Example 136

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