A purchase rate is purchases divided by recipients, so calculate the two rates in Desmos. Then check whether each statement describes the customers tested or promises a result for all customers. Random selection helps a sample represent a larger group, but a sample result is not a guarantee about that group.
Hints
- Hint 1
A purchase rate is the number of purchases divided by the number of recipients. The groups have the same number of recipients, so how do their purchase rates compare?
- Hint 2
A sample is the group actually tested. A rate measured in that group is a fact about those customers, but is the same result guaranteed outside the experiment?
- Hint 3
Random assignment means chance decides who receives each subject line. The prompt says customers were randomly selected, but random assignment is not stated. What does that leave unproved about sending B?
Step-by-step
Compare the rates, then check the reach of each claim
Step 1Calculate each purchase rate
A purchase rate is purchases divided by recipients. Type and in Desmos, using each group’s recipients as its denominator. Desmos shows for A and for B.
- Step 2
Check the claim about the tested customers
is greater than , so B had the higher purchase rate among the customers in the experiment. Statement I describes those customers, so it must be true.
- Step 3
Check the claim about all customers
Random assignment means chance decides who gets A or B; the prompt says customers were randomly selected, but doesn’t say the subject lines were randomly assigned. So the results alone don’t establish that sending B caused the gap. Even with random assignment, a difference measured in a sample isn’t a guarantee for all customers. Statement II need not be true, so only I must be true. Choice B.