Introduction to Science and the Scientific Method

What is the control group in this experiment?

Consists of the 25 plants that are receiving plain water

scientists

collect and organize information in a careful, orderly way, looking for patterns and connections between events.

An experiment is based on the comparison between a __________________ with an ________________________. a) these 2 groups are identical except for one factor. b) the control group serves as the comparison. It is the same as the experiment group, except that the one variable that is being tested is removed. c) the experimental group shows the effect of the variable that is being tested.

control group with an experiment group

In a _________________, only one variable is changed at a time. All other variables should be unchanged or "controlled".

controlled experiment

the independent variable is the variable that is:

deliberately changed by the scientist

qualitative data are...

descriptions and involve characteristics that cannot be counted.

Example: In order to test the effectiveness of a new vaccine, 50 volunteers are selected and divided into 2 groups. One group will be the control group and the other will be the experimental group. Both groups are given a pill to take that is identical in size, shape, color, and texture. Describe the control group:

even though the volunteers are given identical looking pills, the control group will not actually receive the vaccine.

scientists propose ______________ that can be ___________ by examining evidence.

explanations, tested

quantitative data are...

numbers that are obtained by counting or measuring.

how is science done? 1. science begins with an ___________. This is the process of gathering information about events or processes in a careful, orderly way. 2. __________ is the information gathered from making observations.

observations, data

the dependent variable is the one: The dependent variable is the data we collect during the experiment. This data is collected as a result of changing the independent variable.

observed during the experiment

A controlled experiment works with ____________. If several variables were changed at the same time, the scientist would not know which variable was responsible for the observed results.

one variable at a time

What is the difference between the independent and the dependent variables in an experiment?

The independent variable is the variable that is deliberately changed by the scientist. The dependent variable is the one observed during the experiment. The dependent variable is the data we collect during the experiment.

What is the experimental group in this experiment?

The other groups of 75 plants that are receiving various concentrations of fertilizer.

hypothesis

a possible explanation to the question or problem

a hypothesis is a...

a scientific explanation for a set of observations.

It is simply a prediction and has not yet been_________.

proven or disproven

The evidence from the experiment is used to determine if the hypothesis is ___________________________. Experiments must be repeated over and over. When repeated, the results should always be the same before a valid conclusion can be reached.

proven or disproven

It must be stated in a way that is ___________. A statement is considered this if evidence can be collected that either does or does not support it.

testable

What variable is being changed in this experiment?

the amount of fertilizer received by each group of plants

Describe the experimental group:

this group will receive the vaccine.

The factors in an experiment that can be changed are called ___________. Some examples would be: changing the temperature, the amount of light present, time, concentration of solutions used.

variables

What variable is being changed?

whether or not the pill contains the vaccine

What variables must be kept constant in this experiment?

All plants must receive the same amount of fluid each day and the same amount of sunlight. All plants are grown in the same size pot and the same temperature.

Why is it important to repeat the experiment many times?

Experiments should be repeated to see if the same results are obtained each time. This gives validity to the test results.

In a "controlled experiment", why must all of the variables, except one, be kept constant throughout the experiment?

If several variables were changed at the same time, the scientist would not know which variable was responsible for the observed result.

Why is it so important that a scientist accurately describes the procedure used in the experiment?

It allows other scientist to repeat the experiment and verify the results.

Why is it important to have a large sample size in any experiment?

It is important to test a large sample in order to get a true picture of the results of the experiment. If the sample size is too small an inaccurate conclusion may be reached. Results obtained by testing a large number of individuals would be much more accurate than if only a few individuals had been tested.

In the above example, what is the independent variable?

It is the addition of the vaccine to the pills that were given to the volunteers.

You want to determine the effects of a certain fertilizer on the growth of orchids grown in a greenhouse. Materials that are available to you include: greenhouse, 100 orchid plants, water, fertilizer, and soil. You want to know if the orchids will grow best with a weak concentration of fertilizer, a medium concentration of fertilizer, or a high concentration of fertilizer. How will you design an experiment to test different concentrations of this fertilizer? State you hypothesis:

Since there's 4 plants I think the one that has medium fertilizer is going to do good because high fertilizer might have too much, the low fertilized plant might not have enough and the one that doesn't have fertilizer at all will die.

How will you set up a controlled experiment?

The 100 plants will be divided into 4 groups as follows: Group 1: 25 plants will receive plain water Group 2: 25 plants will receive a weak concentration of fertilizer Group 3: 25 plants will received a medium concentration of fertilizer Group 4: 25 plants will receive a high concentration of fertilizer Then the plants will be watered daily. Over a period of a month, the plants will be measured to see which ones grew the tallest.

What is the importance of the control?

The control shows what will happen when the experimental factor is omitted. Without the control, there would be no basis for comparison and you would not know how the experimental factor effected the results.

How is the theory different than the hypothesis?

The hypothesis is a "educated guess" that is testable through observations and experimentation. A theory is a broad statement of what is believed to be true based on many experiments and considerable amounts of data.

A theory may be formed after the hypothesis has been tested many times and is supported by much evidence. Theory- A theory is supported by considerable evidence.

a broad and comprehensive statement of what is thought to be true

the scientific method is:

a series of steps used by scientists to solve a problem of answer a question.

In the above example, what is the dependent variable?

the observed health of the people receiving the pills

What variables are kept constant?

the size, shape, color, and texture of the pill