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Science is the systematic study of nature that helps us to understand natural phenomena and how it affects the environment and living things. Science discoveries help us to understand and appreciate our environment and improve the quality of life. There is a need for a rational and systematic method to investigate and study certain natural phenomena or scientific developments. In order to avoid failure, scientist should have an aim and acceptable guidelines to carry out researches or experiments so that the results are acceptable, reliable and convincing.

Steps in the Scientific Investigation Method

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Observing Phenomena

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Most scientific investigations begin with observations. The phenomenon should be observed carefully and all facts related to it should be written down clearly.

Identifying Problems

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The final task in a scientific investigation is to identify the problem that is to be investigated. We must determine what we want to find out and why the investigation needs to be carried out. The problem is normally identified through observations and is based on certain facts. Problems are usually expressed in statement based on certain situations.

For example:

• Situation: A plant grows under sunlight.
• Problem statement: How is the growth of the plant affected by sunlight?
• Situation: A ball is rolling down a slope.
• Problem statement: How of the plant is the growth of the plant affected sunlight?

Identifying Variables

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Variables are factors that will affect the result of an experiment. For example, it an experiment to investigate the amount of energy lost during the transmission of electrical energy through a cable. The amount of energy lost depends on factors such as voltage, electric current and the size of the cable. All these factors including the amount of energy lost are variables in this investigation. The three variables that have to be identified in a scientific investigation are the manipulated variable, responding variable and controlled variable.

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The manipulated variable is the factor that is being studied in an experiment. The responding variable is the variable that changes or reacts as a result of changes to the manipulated variable. The controlled variable or fixed variable is kept constant and does not change. In a simple pendulum experiment, the manipulated variable is the length of a pendulum. The responding variable is the time taken for the pendulum to make 20 complete oscillations. The controlled variable is the mass of the pendulum.

Some manipulated variables can be measured or need to be measured. When the variable does not need to be measured, terms like large, small and smaller are used to represent the manipulated variable, for example, a larger surface area and smaller surface area.

Forming Hypotheses

A hypothesis is a proposed explanation for certain facts or to provide a basis for further investigation. It is a general statement regarding the relationship between the manipulated variable and responding variable. For example, in an experiment to investigate how the extension of a spring is affected by the force acting on it. The hypothesis is the larger the force acting on it, the longer the extension of the spring. A hypothesis is usually formed based on scientific knowledge and assumptions. More than one hypothesis can be proposed in an experiment but every hypothesis must be tested to prove its validity. This can be done by conducting investigations or experiments.

Planning Investigations

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Before a scientific investigation is carried out, some researches should be done to find out more facts that are related to the problem that is to be investigated. In order to obtain precise and accurate results, suitable location or area, such as in the dark room, in open air or in a laboratory. When planning an investigation, the following need to be considered:

(a)  Controlling the variables

The method of controlling the manipulated variable the method of measuring the responding variable and the method of keeping the controlled variable constant have to be determined.

(b) Determining the apparatus and the materials needed. For example, a clinical thermometer is not suitable to be used when the temperature of the water that is to be measured is in the range of 0°C to 100°C.

(c)  Determining the procedure. The correct the procedure has to be followed to produce accurate, reliable results. Each step in the procedure should be described clearly.

(d) Determining the method of data collection and data analysis. This has to be planned to ensure that the data collected are precise.

Carrying Out Investigations

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The experiment that is to be carried out should be based on the procedures planned.

Observing and Collecting Data

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Observations and measurements that are collected during an experiment are known as data. Data that are based on measurements and are stated in numbers are known as quantitative data. Examples of quantitative data are weight of an object and the number of organisms in a habitat. Quantitative data should have units. A quantitative datum without a unit is meaningless. For example, the length of a wire is 7. This does not provide accurate information because 7 can mean 7 cm or 7 m. Table below shows some examples of quantitative data, their units and the measuring instruments used to measure the data:

Quantities data	Units	Measuring instruments
Length	Meter (m), centimeter (cm)	Meter rule, measuring tape
Time	Second (s), minute	Stopwatch, stop-clock
Temperature	Celsius (°C)	Thermometer
Mass	Kilogram (kg)	Lever or beam balance
Electric current	Ampere (A)	Ammeter

Data that are not based on measurements and cannot be stated in numbers are known as qualitative data. Observations such as smells, tastes, textures and sounds are examples of qualitative data. All data collected in an experiment must be recorded. The data may be presented in the form of tables, pie charts, bar charts, histograms or line graphs.

Table

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A table is a simple and organized way to display data. Data that are presented in a table can be read and analyzed easily. A table is displayed either in vertical or horizontal form. Table below shows a horizontal table. The first row represents the manipulated variable and the second row represents the responding variable. Table below shows a vertical table. The left column represents the manipulated variable while the right column represents the responding variable.

Weight (N)	Length of spring (cm)

Bar Chart

A bar chart is used to show collective data of different categories. The width of each bar is equal, whereas the height or length depends on the frequency of data collected.

Pie Chart

A pie chart is used when data is shown in fractions or percentages. A pie chart is a circular chart divided into sections. The angle of each sequent is proportional to the percentages it represents. The area (or angle) of each sector gives the proportion of the category of data it represents. The pie chart in photograph below shows the resource usage – actual..

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Histogram

A histogram is used to display the frequency or distribution of data. Photograph below shows the resource histogram.

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Line Graph

A line graph is used to show the relationship between the responding variable and manipulated variable. The manipulated variable is represented by the x-axis whereas the responding variable is represented by the y-axis. Usually, at least five pairs of readings or values must be collected to plot a graph. Both axes must be given.

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Analyzing and Interpreting Data

Analyzing data includes evaluating the data and determining the relationship between the manipulated and responding variables. After analysis, the data is then interpreted logically and objectively in order to derive accurate information. Photograph below shows  the interpretation made about the relationship between voltage and direct current flowing through a resistor.

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Interpretation:

• The voltage across the resistor is directly proportional to the current.
• The gradient of the straight line represents the resistance of the resistor.

Interpretation: The larger the direst current, the larger the voltage across the resistor.

Making Conclusions

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The conclusion of an experiment is statements which will be either accept or reject the hypothesis. The conclusion is made based on interpreted data. The weakness and limitations of the investigation will restrict the conclusion that is made. Example of a conclusion:

Experiment: To study how the transpiration of a plant is affected by the presence of sunlight.

Hypothesis: The presence of sunlight will increase the rate if transpiration of a plant.

Conclusion: Sunlight increases the rate of transpiration of a plant. The hypothesis is accepted.

Writing Reports

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A report must be completed and include all the relevant information pertaining to the experiment. It must be precise and objective. The past tense in the passive voice should be used when writing a report, for example the solid was weighed and completely immersed in water. Table below shows a description of the items in a complete report.

Items	Explanation
Aim	To investigate the reason for the experiment. For example: To study … To verify … To determine …
Problem statement	Identifying the problem in the investigation: How does temperature affect the rate of evaporation of water? How does the length of pendulum affect the rate of evaporation of oscillation of a pendulum?
Hypothesis	Predicting the results of the experiment For example: The longer the distance, the longer the time taken.
Variables	Determining the manipulated, responding and controlled variables.
Apparatus and materials	Listing all the apparatus and materials required for the experiment so that the observation or reading for the manipulated and responding variables can be made.
Procedure	A complete and detailed description of the steps taken in the experiment, including the set-up of the experiment.
Observations/ results
Analysis and interpretation of data	Evaluating the data, and determining the relationship between two variables.
Conclusion	Making a statement that either accepts or rejects the hypothesis

The Importance of the Scientific Investigation Method

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The scientific investigation method is important as it provides a systematic and complete way to acquire scientific knowledge. It also teaches us to think critically and analytically. For example, we need to be critical and creative when we are forming a hypothesis for an experiment. The method also provides us with reliable, useful results. This is because the results were obtained from experiments that were carried out systematically.