Scientific Method Review

With Your Partner… What is the difference between a hypothesis, a theory, and a law? What is the difference between a control group and an experimental group? What is the difference between an independent variable and a dependent variable? What is a constant?

Identify: IV, DV, constants, experimental group, control group Maria wants to know if non-stick cooking spray really works. She fries ten Grade A eggs without any spray, then scrapes the pan and weighs the amount of egg stuck to the bottom. Each time she carefully washes the pan between eggs with dish soap. She repeats the procedure in exactly the same way ten times more, but this time she sprays the pan for two seconds with non-stick cooking spray before adding the eggs.

Identify: IV, DV, constants, experimental group, control group Jose wants to know if caffeine affects the heart rate of daphnia. He observes a daphnia and counts its heart rate for three minutes. He then adds 5 milliliters of a solution of caffeine dissolved in water to the container with the daphnia, and measures the heart rate for another three minutes. He repeats this process with a total of twenty daphnia.

Identify: IV, DV, constants, experimental group, control group Nakeshia wants to know if water freezes faster with sugar in it. She prepares two ice trays with 20 milliliters of water in every other well. She then dissolves 30 grams of sugar in a gallon of water and puts 20 milliliters of the solution in each of the remaining wells. Nakeshia sets a timer, puts the ice trays in the fridge, and checks on the cubes every ten minutes until all are frozen.

With Your Partner… What are the components of a good experiment?

Good Experiments… Have a hypothesis that can be supported or rejected. Have detailed, repeatable instructions. Have only one independent variable. Have a large sample size. Have a control group when the point of the experiment is to determine the effect of something. Are shared with others.

What’s Wrong? Rita wanted to find out which of two movies is more popular. She went to Palm Valley Cinema and asked fifty people coming out of Movie A to rate how much they enjoyed the movie on a scale of one to five. After that she went to Harkins theater, where Movie B is playing, and did the same thing. She averaged the scores and decided that Arizonans think that Movie B is better.

What’s Wrong? Kerri wanted to know which brand of air freshener works best. She put Renuzit in the hall bathroom and Glade in the master bathroom. Twice daily at eight AM and PM she rated the smell in the bathrooms on a scale of one to five. She concluded that Renuzit works best.

With Your Partner… How do you decide to accept or reject your hypothesis? Psychics…