Researchers Selected a Simple Random Sample of 4048 Medical Records

Multiple Choice

Researchers selected a simple random sample of 4048 medical records of adults diagnosed with gum disease. In all, 2226 were current smokers, 891 were former smokers, and 931 never smoked regularly. Their research question is, Do these data indicate that gum disease is equally likely regardless of smoking status? Is the chi-square test valid in this situation?

A) No, because the study is not a randomized experiment.
B) Yes, because the sample size is large.
C) Yes, because the sample is random and the observed counts are large enough.
D) Yes, because the sample is random and the expected counts are large enough.