Calculate a 95 confidence interval for the differ ence of th
     Calculate a 95% confidence interval for the differ.. ence of the mean tensile strengths of the two rubl,e compounds. State your assumptions. 7.2 - 14. Let S   and S    be the respective variances of two independent random samples of sizes n and m from N(    ) and N(   ). Use the fact that F =              has an F distribution, with parameters r1 = m - 1 andr2 = n - 1,to rewrite P(c  
  
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