Amedical researcher studies the correlation between the number of hours spent at office jobs and the incidence of chronic back ache. which statement best describes why the investigation is an observational study? a) the researcher does not use a control group. b) the researcher does not intervene to vary conditions. c) it is not possible to obtain a random sample of office workers. d) it is not possible to establish a cause-effect relation between the variables.

B) The researcher does not intervene to vary conditions.

Step-by-step explanation:

The other person is wrong, I put C the first time I did a test containing this question and submitted it. But then I retried my incorrect responses and this was one of the incorrect responses. So I did the math again and I got B, and I submitted the test again and it was correct.

not enough information

step-by-step explanation:

we cannot know this, because the other students could have handed out 10 flyers, or they could have handed out 100. one way, the mean would go up, and another way, the mean would go down.

80% of the cookies

step-by-step explanation: