Complete question:
Tina asks the question “Does caffeine increase the heart rate of an earthworm?” In Test 1, she measures the heart rate by looking at the earthworm under a microscopes, the earthworm has a heart rate of 50 bpm (beats per minute). In Test 2, she places a few drops of caffeine on the earthworm’s skin and measures the rate again. In this test, the heart rate is 68 bpm.
1) What is the control group?
2) What is the experimental group?
3) What is the independent (manipulated) variable?
4) What is the dependent (responding) variable?
5) What should Tina's conclusion be?
Individuals from test 1Individuals from test 2CaffeineHeart rateTina´s hypothesis is correct. Caffeine increases the heart rate of an earthworm. Â
Explanation:
During an experiment, data from an experimental group is compared with the data from a control group. Both groups are selected from the same pool or population, so they are identical in all aspects except for the independent variables. Â
The control group is used to identify any other factors influencing the results obtained in the study, apart from the modified variables of the treatment.
The experimental group is the one affected by the experimental procedure or treatment. The researcher voluntarily changes the independent variables in the experimental group to observe how they affect the group under study. These variables are kept constant in the control group, not influencing the results, while the experimental group receives the treatment. There can be several experimental groups. Â
Independent (manipulated) variable: Refers to all the variables in an experiment that provoke a response in another variable. An independent variable is the one that changes or is controlled and modified in the experiment to analyze how another variable responds to it. It changes to analyze its effects on the dependent variable. Usually, the independent variable is represented by the X letter. Â
Dependent variable: Refers to the variable, which response depends on any change in the independent variable. It represents a quantity of something which value depends on how the independent variable is modified. The change in the dependent variable might be proportional or inversely proportional to the change in the manipulated variable. It is usually represented using the letter Y. Â Controlled variable: Refers to the variables that have no influence on the results. These variables do not affect the change in the dependent variable values. Â
1) What is the control group?
Individuals from test 1 compose the control group. They are not affected by the treatment. Tina just uses them to measure the normal heart rate and to compare them with individuals from test 2.
2) What is the experimental group?
Individuals from Test 2 compose the experimental group. They are affected by the treatment. Tina drops caffeine on their skin to see how it affects the worms.
3) What is the independent (manipulated) variable?
Caffeine is the independent variable. Tina manipulates the number of drops she places on the worm´s skins.
4) What is the dependent (responding) variable?
Heart rate is the dependent variable. Tina evaluates how the heart rate changes in individuals with or without caffeine.
5) What should Tina's conclusion be?
Caffeine increases the heart rate of an earthworm. It changes from 50 to 68 bpm. Tina´s hypothesis is correct.
