TOPIC: Interpretation of variable data
To the student:
A. Let us recall our earlier enquiry into the cell nucleus. We were told then that all the cell fragments which lacked a nucleus soon died. We were also told that all the cell fragments in the experiment which retained a nucleus recovered and went on to live normally.Now, in the experience of biologists, such neat, either/or results occur rarely, if ever. Rather, results are more likely to look like these:
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Question #1
If you had to make a positive interpretation of the data about the im-portance of the nucleus, what would you say? What is there about the data which could make you feel uneasy about the interpretation you made?
To the student:
B. Let us assume that the scientists who did the work stated their interpretation as follows:"Our experiment was judged satisfactory and was terminated at the thirtieth day. Our data indicate that the nucleus is normally necessary for the continued life of the cell."Now as we can see, the conclusion drawn by the scientist "goes beyond the data, ["Data" are the recorded facts from which we try to derive an answer to a question, a solution to a problem.] for we see that not only did some non-nucleated fragments live for three days, but that a number of nucleated fragments died, some after one day, more after two days, still more in ten days, and so on. It is entirely possible that if the experiment had been extended for sixty days or more, many more nucleated fragments might have died.
How, then, can we defend the statement with which the scientist concluded his piece of research? The general answer is that one experiment can rarely, if ever, prove a scientific statement beyond any shadow of doubt. There is always some doubt, and successive experiments try to remove one doubt after another.
In short, it is a little bit misleading to say that a scientist draws a conclusion from his data. For his summing up is rarely a conclusion, an end to research on that subject. Rather, it is a beginning or a continuation. It is more informative to say that a scientist interprets his data. He expects other scientists to check him, refine his interpretation, and extend it. For science it a social, cooperative enterprise.
Let us go back to our new data about the number of nucleated and non-nucleated fragments which survive. A more cautious scientist complained to our biologist that his interpretation of his data was unacceptable until he gave at least one reasonable explanation for the death of so many nucleated fragments.
Question #2
Come to the defense of our biologist. Provide him with such an explanation.*Hint 1: Remember how the nucleated fragments were obtained.*Hint 2. Think of what probably would happen if you tried to nur-ture 10 baby chicks or 100 baby kittens to maturity.
To the student:
C. There are cells which normally contain no nucleus and yet live a long time. Suppose for the moment that our experimenter is right&emdash;that in cells with a nucleus, there is something in the nucleus indispensable to survival.Question #3
How would you explain the healthy long lives of cells that do not have nuclei?
To the student:
D. One interesting example of non-nucleated cells is the mature human red blood cell. The nucleus degenerates during the development of the cell. Even that "something" in the nucleus degenerates.Question #4
In view of this information, what would you expect to be the length of life of such cells?
