Handbook : Thinking Critically
Scientists try to make careful and accurate observations. When possible, they
use instruments such as microscopes, thermometers, and balances to make observations.
Measurements with a balance or thermometer provide numerical data that can be
checked and repeated. Other observations are made using your senses. The basis
of all scientific inquiry is observation.
Scientists often make inferences based on their observations. An inference is
a conclusion about what was observed. When making an inference, be certain to
use correct data and observations. Analyze all of the data that you've collected.
Then, based on everything you know, draw a conclusion about what you've observed.
If possible, investigate further to find out if your inference was correct.
drank a glass of orange juice after the volleyball game, you observed that the
orange juice was cold. You might infer or conclude that the juice was cold because
it had been made earlier in the day and had been kept in the refrigerator. The
only way to be sure which inference is correct is to investigate further.
Observations can be analyzed by looking at the similarities and the differences
between two or more objects or events that you observe. When you look at objects
or events to see how they are similar, you are comparing them. Contrasting is
looking for differences in objects or events. Compare and contrast the nutritional
value of two candy bars in Figure 13.
Cause and Effect
Have you ever watched something happen and tried to figure out how or why it came
about? If so, you have observed an effect and inferred a reason for the event.
The event is an effect, and the reason for the event is the cause.
that every time your teacher fed the fish in a classroom aquarium, he or she tapped
the food container on the edge of the aquarium. Then, one day your teacher just
happened to tap the edge of the aquarium with a pencil. You observed the fish
swim to the surface of the aquarium to feed, as shown in Figure 14.
the effect, and what would you infer to be the cause? The effect is the fish swimming
to the surface of the aquarium. You might infer the cause to be the teacher tapping
on the edge of the aquarium. In determining cause and effect, you have made a
logical inference based on your observations. Perhaps the fish swam to the surface
because they reacted to the teacher's waving hand or for some other reason. When
scientists are unsure of the cause of a certain event, they plan experiments to
determine what causes the event. Although you have made a logical conclusion about
the behavior of the fish, you would have to perform an experiment to be certain
that it was the tapping that caused the effect you observed.