Rockwell hardness index for steel

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The Rockwell Hardness Index for Steel is determined by pressing a diamond point into the steel and measuring the depth of penetration. For 50 specimens of a steel alloy, the Rockwell hardness index averaged 62 with a standard deviation of 8. The manufacturer says this alloy has an average hardness index of at least 64. Is there enough evidence to refute what the manufacturer has said? with a significance level of 1%?

The test statistic is:

The critical value is given by:

The decision is:

The decision will be worded as follows: We do not reject Ho or We reject Ho

Reference no: EM132529651

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