Question

To be considered 18-karat (18K) gold, a piece of jewelry must be made of 75% pure gold. The higher the karats, the more valuable a piece of jewelry. A jewelry designer is purchasing a large quantity of 18K gold from a new supplier. To see whether the new supplier is being dishonest about the karat rating in the shipment, the designer melts a random sample of the gold and conducts a hypothesis test with H0: The proportion of metal that is gold is 75%, and Ha: The proportion of metal that is gold is less than 75%. What are a Type I error and a Type II error in this context?

Type I error: The gold shipment truly is made of 75% gold, but the designer concludes that it is made of less than 75% gold.
Type II error: The gold shipment truly is made of less than 75% gold, but the designer concludes that it is made of 75% gold.
Type I error: The gold shipment truly is made of 75% gold, but the designer concludes that it is made of less than 75% gold.
Type II error: The gold shipment truly is made of less than 75% gold, and the designer concludes that it is made of less than 75% gold.
Type I error: The gold shipment truly is made of 75% gold, and the designer concludes that it is made of 75% gold.
Type II error: The gold shipment truly is made of less than 75% gold, but the designer concludes that it is made of 75% gold.
Type I error: The gold shipment truly is made of less than 75% gold, but the designer concludes that it is made of 75% gold.
Type II error: The gold shipment truly is made of 75% gold, but the designer concludes that it is made of less than 75% gold.

Answer 1

Answer:

Type I error: The gold shipment truly is made of 75% gold, but the designer concludes that it is made of less than 75% gold.

Type II error: The gold shipment truly is made of less than 75% gold, but the designer concludes that it is made of 75% gold.

Step-by-step explanation:

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Answer 2

The type I error and type II errors for this condition are given by: Option A:

• Type I error: The gold shipment truly is made of 75% gold, but the designer concludes that it is made of less than 75% gold.
• Type II error: The gold shipment truly is made of less than 75% gold, but the designer concludes that it is made of 75% gold.
  

What are type I and type II errors?

The Type I error is false positive (returning the test result as positive, which means, rejecting the null hypothesis(conclusion of rejection of null hypothesis is called positive test result) when its incorrect).

The Type II error is false negative (returning the test result as negative, which means, accepting the null hypothesis(assuming negative test result, so no flaw in null hypothesis from the perspective of test) when its wrong).

For this case, the hypotheses laid down are:

• Null hypothesis: H₀ : The proportion of metal that is gold is 75%,
• Alternate hypothesis: H₁ :  The proportion of metal that is gold is less than 75%.

Thus, we get:

Type I error = False positive = Falsely accusing null hypothesis to be incorrect = Concluding that the proportion of metal that is gold is less than 75% when actually the proportion of gold is 75%.

Type II error = False negative = Falsely accepting the null hypothesis = Concluding that the proportion of metal that is gold is 75% when actually the proportion of gold is less than 75%.

Therefore, the type I error and type II errors for this condition are given by: Option A:

• Type I error: The gold shipment truly is made of 75% gold, but the designer concludes that it is made of less than 75% gold.
• Type II error: The gold shipment truly is made of less than 75% gold, but the designer concludes that it is made of 75% gold.

Learn more about type I and type II errors here:

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