Scientific method and data analysis

The scientific method is the procedure followed by scientists to study problems and reach valid conclusions.

The scientific method follows a series of steps, which are:

1. Observation

2. The hypothesis

3. Experimentation

4. Analysing the results

5. Defining laws and theories

6. Publishing the results

Think

Look at these two containers of water:

Which one do you think will evaporate first?
Do you dare to formulate a hypothesis?
How could you verify that hypothesis?

Sometimes, in science, the scientific method cannot be followed precisely. For example, in astronomy you can only measure what happens in the universe; you cannot experiment with it. You have to continue observing and measuring to find out if your hypothesis true.

Here's a reminder of the six phases of the scientific method.

How much do you know about the scientific method?

Does a hypothesis always have to be verifiable?

How much do you know about the scientific method?

Does a hypothesis always have to be verifiable?

Can you put the steps of the scientific method in the right order ?

Which of these can predict unknown phenomena?

What is a scientific law?

To be confirmed, a hypothesis must be true in various conditions, so many times several experiments are performed with changes to some of the initial conditions.

Therefore, lots of different data is obtained. In order to analyse it, it is necessary to organise it in tables and graphs.

Tables

Graphs

A table allows us to organise data in rows and columns:

In each column the data of a characteristic of the problem is represented, that is, of a variable.
In each row the values of each variable are arranged for a measurement.

For example, if we measured the speed with which two balls of different mass go down an inclined plane we would obtain data like this:

**Ball A (50 g)**
Length (m)	Time (s)
0.25	0.34
0.50	0.48
0.75	0.59
1.00	0.68

**Ball B (22 g)**
Length (m)	Time (s)
0.25	0.34
0.50	0.48
0.75	0.59
1.00	0.68

The graphs show the data obtained in a visual way. For example, the graphs show the relationship between two variables and allow us to know values that we have not measured:

Interpolating data is to obtain intermediate values to other measured ones.
Extrapolating data is to obtain values outside the range of those that have been measured

For example, for Ball A, a graph like this may be obtained:

In an experiment a robot is programmed to move at different speeds, and in each case the time it takes to travel a previously set distance is measured. Observe the chart.

v (m/s)	20	16	10	5	4	2	1.25
t (s)	1	1.25	2	4	5	10	16

a) Let's represent the data in the corresponding graph.

b) Which law can be deduced from this data?

The graph shows a rectangular hyperbolic curve, therefore:

We can express the law as "The speed of the robot is inversely proportional to the time that it takes in to travel a determined distance".
The mathematical equation for this law is $v por t igual k$ .
In all measurements, the product of $v por t igual 20$ , which is the distance it travels in all cases. That's why it coincides with the expression that relates speed with time and space travelled: $v por t igual d$

c) How fast does the robot go after 8 s?

In the graph we read that when t = 8 s, v = 2.5 m/s.

This result can also be obtained by substituting in the mathematical expression:

$v igual fracción d entre t igual fracción numerador 20 espacio normal m entre denominador 8 espacio normal s fin fracción igual 2.5 espacio normal m dividido por normal s$

When we plot the data in a graph, the resulting lines are telling us the relationship between magnitudes.

Ascending straight line

Descending straight line

Rectangular hyperbolic curve

An ascending straight line represents direct proportionality between the two variables represented.

There are two possibilities:

The line goes through the origin.
The line doesn’t go through the origin.

Line goes through the origin

Line doesn't go through the origin

Mathematical expression

y = k · x

Mathematical expression

y = k · x + n

A descending straight line means that the decrease of one variable is directly proportional to the other variable.

Mathematical expression y = -k · x + n

In this example, the graph shows that one variable is inversely proportional to the other one. The higher variable x is, the lower variable y will be.

Mathematical expression y · x = k

Imagine you are studying the phenomenon of rainbows.

What questions can you ask to help you understand it?
Formulate some hypotheses to explain this phenomenon.
Don't worry about whether these hypotheses are true or not. What's important is that they're rational and verifiable.

(0 words)

Do the following statements correspond to a scientific hypothesis?

The height reached by a body thrown upwards depends on the color of the object being thrown.

Yes, it is a scientific hypothesis.

No, it is not a scientific hypothesis.
Correct answer

Wrong answer
The height reached by a body thrown upwards depends on the initial velocity we give it.

Yes, it is a scientific hypothesis.

No, it is not a scientific hypothesis.
Correct answer

Wrong answer
The height reached by a body thrown upward is related to what the person throwing it thinks.

Yes, it is a scientific hypothesis.

No, it is not a scientific hypothesis.
Correct answer

Wrong answer

Taking into account the phases of the scientific method:

a) Explain the difference between a law and a hypothesis.

b) Explain the difference between a law and a theory.

c) Give an example for each of these concepts.

(0 words)

Look at the graph and choose which of the following statements is correct.

Look at the table below:

Circumference (mm)	73.01	76.17	62.02	66.73	58.88
Diameter (mm)	23.25	24.25	19.75	21.25	18.75

Plot a graph in your notebook of the length of the circumference versus the diameter. Take a picture of it and complete the exercise by attaching your file.

My files

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What's the relationship between the two magnitudes?

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What is the scientific method?

Look at these two containers of water:

Which one do you think will evaporate first?

Do you dare to formulate a hypothesis?

How could you verify that hypothesis?

Are there any shortcuts?

The scientific method: a summary

Here's a reminder of the six phases of the scientific method.

Observation

Let's test

How much do you know about the scientific method?

Does a hypothesis always have to be verifiable?

Let's test

How much do you know about the scientific method?

Does a hypothesis always have to be verifiable?

Analysing the results

What's the robot doing?

How to interpret a graph

When we plot the data in a graph, the resulting lines are telling us the relationship between magnitudes.

Line goes through the origin

Line doesn't go through the origin

How are rainbows formed?

Imagine you are studying the phenomenon of rainbows.

Are they hypotheses?

Do the following statements correspond to a scientific hypothesis?

Hypotheses, laws and theories

Analyse the data of a graph

Look at the graph and choose which of the following statements is correct.

Plot the data on a graph

Look at the table below:

Plot a graph in your notebook of the length of the circumference versus the diameter. Take a picture of it and complete the exercise by attaching your file.

What's the relationship between the two magnitudes?

Now I know