Testing electronic circuits. Japanese researchers have developed a compression–depression method of testing electronic circuits based on Huffman coding (IEICE Transactions on Information & Systems, Jan. 2005). The new method is designed to reduce the time required for input decompression and output compression—called the compression ratio. Experimental results were obtained by testing a sample of 11 benchmark circuits (all of different sizes) from a SUN Blade 1000 workstation. Each circuit was tested with the standard compression–depression method and the new Huffman-based coding method and the compression ratio recorded. The data are given in the next table.

a. Compare the two methods with a 95% confidence interval. LO3 Which method has the smaller mean compression ratio?

b. How many circuits need to be sampled in order to estimate the mean difference in compression ratio to within

.03 with 95% confidence.

Circuit Standard Method Huffman Coding Method 1 .80 .78 2 .80 .80 3 .83 .86 4 .53 .53 5 .50 .51 6 .96 .68 7 .99 .82 8 .98 .72 9 .81 .45 10 .95 .79 11 .99 .77