4 A shelf at the grocery store
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Answer:
The 95% confidence interval for the proportion of all boards in this shipment that fall outside the specification is (1.8%, 6.2%).
Step-by-step explanation:
Let <em>X</em> = number of boards that fall outside the most rigid level of industry performance specifications.
In a random sample of 300 boards the number of defective boards was 12.
Compute the sample proportion of defective boards as follows:
The (1 - <em>α</em>)% confidence interval for population proportion <em>p</em> is:
The critical value of <em>z</em> for 95% confidence level is,
*Use a <em>z</em>-table.
Compute the 95% confidence interval for the proportion of all boards in this shipment that fall outside the specification as follows:
Thus, the 95% confidence interval for the proportion of all boards in this shipment that fall outside the specification is (1.8%, 6.2%).