Question

identify the sample method used and whether it is biased or unbiased. then determine whether the inference is valid. (examples 3 and 4)

1. to evaluate customer satisfaction, a grocery store manager gives double coupons to anyone who completes a survey as they enter the store. the store manager determines that customers are very satisfied with their shopping experience in his store.
2. a member of the cafeteria staff asks every fifth student leaving the cafeteria to rank 5 entrees from most favorite to least favorite. she finds that pizza is one of the favorite entrees.

test practice

1. multiselect to evaluate the defect rate of its lenses, a camera lens manufacturer tests every 100th lens off the production line. out of 1,000 lenses tested, one lens is found to be defective. the manufactur concludes that 3 lenses out of 3,000 will be defective. select all of the statements that are true about the sampling method.

□ this scenario is a systematic random sample.
□ the sampling method is biased.
□ the inference is valid.
□ this scenario is a convenience sample.
□ the sampling method is unbiased.

Explanation:

• Systematic random sample: A systematic random sample is a type of probability sampling method where elements are selected from an ordered population at regular intervals. In this case, every 100th lens is tested, which follows a systematic pattern.
• Unbiased sampling method: An unbiased sampling method is one where every element in the population has an equal chance of being selected. Since the manufacturer is testing every 100th lens off the production line, each lens has an equal probability of being selected, making the sampling method unbiased.
• Valid inference: A valid inference is one that is based on a representative sample. Since the sampling method is unbiased and systematic, the inference that 3 lenses out of 3,000 will be defective is valid.

Answer:

• This scenario is a systematic random sample.
• The sampling method is unbiased.
• The inference is valid.