Organizing Information Thinking Critically • Observing and Inferring • Comparing and Contrasting • Recognizing Cause and Effect Practicing Scientific Processes
 Skill Handbook :  Thinking Critically
Observing and Inferring

Observing
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.

Inferring
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.

When you 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.

Comparing and Contrasting
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.

Recognizing 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.

Suppose 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.

What is 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.