Solid copper produced by sintering heating without melting a

Solid copper produced by sintering (heating without melting) a powder under specified environmental conditions is then measured for porosity in a laboratory experiment. A sample of n_1= 4 independent porosity measurements have mean 0.22 and variance 0.0010. A second laboratory repeats the same process and gets n_2=5 independent porosity measurements with mean 0.17 and variance 0.0020. Estimate the true difference between the population means for these two laboratories. Place a 2-standard deviation bound on the error of estimation. Construct a 95% confidence interval for the difference between the population means for these two laboratories. Interpret the confidence interval.

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