Question

1. what is a key feature of a well - designed randomized experiment?

a. a survey is distributed before the experiment
b. groups are selected based on prior knowledge
c. every participant receives the treatment
d. participants are assigned to groups by chance

Explanation:

In a well - designed randomized experiment, random assignment is crucial. This means participants are assigned to groups by chance to minimize bias and ensure groups are comparable. Option a is not a key feature, a pre - experiment survey is not essential. Option b goes against randomization as selection based on prior knowledge is non - random. Option c is incorrect as in an experiment there are usually treatment and control groups.

Answer:

d. Participants are assigned to groups by chance