Question

Answer Questions 2.3.

2.3 Devise hypothesis to account for the following observations, and design an experiment or suggest further observations to test your hypothesis.

1. More automobile accidents occur at dusk than at any other time of day
2. When glass tumblers are washed in hot soapsuds and then immediately transferred face downward onto a cool, flat surface, bubbles at first appear on the outside rim, expanding outward. In a few seconds they reverse, go under the rim, and expand inside the glass tumbler
3. In mice of strain A, cancer develops in every animal living longer than 18 months. Mice of strain B do not develop cancer. If the young of each strain are transferred to mothers of the other strain immediately after birth, cancer does not develop in the switched strain A animals, but it does develop in the switched strain B animals living longer than 18 months.

Answer 1

(a) A plausible hypothesis can be that it is rush hour during dusk; people are in a hurry to return home. So it might lead to more accidents. But peak hour is also during the daytime, especially between 8 am and 10 am. People will be in more hurry to rush to their workplace or institutions then. But the data say that more accidents occur during dusk, so it is natural to think that daylight might have something to do with it. Maybe the receding light of the sun (which is ample in the morning peak hours) leads to poorer vision of individuals, thus escalating accident rates. An experiment to test the hypothesis can be to test an individual's eyesight under different lights - natural and artificial, and collect data accordingly to see if there are any losses in vision during waning lights. Another hypothesis can be that during dusk, when people are returning homes, they may be tired. Slacking off while on the steering wheel can lead to accidents. But there won't be very practical methods of experimenting this hypothesis.

(b) When the tumbler is still warm, the air inside it is expanding, pushing the bubbles outside. Gradually, as the tumbler cools, the air begins to contract to reach its equilibrium state, pulling the bubbles inside. As an experiment, one can wash the tumbler in cold soapsuds, in which case it can be predicted that no bubbles would form as there is not much expansion or contraction of air.

(c) It can be seen that strain B babies develop cancer only after being in contact with strain A mothers. So, a hypothesis will be that contact is important. Most likely, strain B babies drink strain a mothers' milk and thus get infected with the cancerous virus. As an experiment to this hypothesis, strain B babies can be denied the milk of strain A mothers and rather be given some different kind of nourishment. Then they are observed for a long duration to see if they develop cancer.