How to Design a Scientific Investigation

RESEARCH QUESTION AND BACKGROUND

HYPOTHESIS AND SCIENTIFIC EXPLANATION

INDEPENDENT AND DEPENDENT VARIABLES

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Complete the following:

• State your IV.
• Choose an IV that is quantifiable (ie. measurable using numbers), no “kinds” or “types”.
• Describe how you will accurately measure and/or control your IV, including the equipment and units you will use.
• Either state that you will collect 25 samples for your IV, OR, select five levels for your IV range, including a control if possible.
• Justify your choice of range using research and/or logic.
• If you can’t choose a logical IV range (maybe for safety or because you don’t have the equipment) explain why.
• State your DV.
• Describe how you will accurately measure your DV, including equipment and units.
• Use SI units (eg. metres, seconds, kilograms).

CONTROLLED VARIABLES

Complete the following:

• Identify the variables that will make your data unreliable if they are not controlled.
• Use scientific reasoning to describe how they would affect your data if not controlled.
• Describe how you will make sure these variables are controlled. Use specific values if appropriate. Remember that you don’t necessarily have keep these variables constant, so long as they’re the same for all test subjects (eg. You don’t need to give plants a constant source of light, just make sure all of the plants get the same amount of light throughout the day.

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AVOID A COMMON MISTAKE

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Don’t write about your independent variable in this section. By definition the independent variable MUST change, whereas controlled variables stay the same.

EQUIPMENT AND MATERIALS

WRITTEN PROCEDURE

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Complete the following:

• Describe your experiment, including enough detail in your procedure that a classmate could replicate it exactly.
• Assume your reader has the same level of knowledge as you. So, don’t over-explain steps. For example, don’t explain the individual steps of using a mass balance or Bunsen burner.
• Include instructions for controlling the controlled variables.
• Include a step that says to take 25 samples, OR, include a step with instructions to test the five different levels of the IV, and include instructions for five repeated trials.
• Consider including a diagram to help your description.

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AVOID A COMMON MISTAKE

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Don’t copy and paste repeated steps. Instead write something like ‘Repeat steps 2-5 using 2mL, 4mL, 6mL and 8mL of water’.

SAFETY, ENVIRONMENT AND ETHICS

Complete the following:

• Identify any important safety, environmental or ethical issues involved in this lab.
• For safety, consider the dangers of any equipment used such as glassware, any chemicals used, any chemicals produced, and any actions that may cause harm to you or anyone else.
• For environmental, consider the effect on the environment of the use, manufacture and disposal of any materials or equipment . Ensure that the amounts of materials you use are as low as possible to avoid unnecessary waste.
• For ethical, consider whether it is ethical to use money and materials for this investigation when it could be used for other things.

RAW DATA

PROCESSED DATA

GRAPH

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AVOID A COMMON MISTAKE

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If you included anything other than numbers and decimal points in the table (excluding the headings), your spreadsheet software will get confused and produce the wrong kind of graph.

INSERT YOUR GRAPH HERE

INTERPRETATION AND EXPLANATION

ANALYSIS OF THE DATA

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Complete the following:

• Use the range of repeated trials to evaluate the repeatability of your measurements.
• Discuss whether the number of repeated trials was sufficient. Justify your answer.
• Discuss whether you had enough levels of the independent variable to see a relationship with the dependent variable.
• Discuss the number of decimal places in your data and what this means for the precision of your measurements.
• Describe any significant qualitative observations and evaluate their effect on your data.
• Evaluate the significance of how well the trendline fits the data.

EVALUATION OF THE METHOD

AVOID COMMON MISTAKES

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There are a few ways in which students often go wrong when evaluating a method. Be careful not to fall into the following traps:

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1. Don’t write about something that happened to you but is unlikely to happen to someone trying to replicate your experiment. For example, if the batteries in your measuring instrument went flat during the experiment, this is not a limitation of the method, since there is no step that says, ‘Make sure the batteries of your instrument go flat’.
2. Only write about aspects of the method that affected your data. It does not affect your data if the experiment was fun, quick or easy.
3. You are expected to carry out the method as it is written in the procedure. If, for some reason you, for example, forgot to control a variable, then this is a problem with your data but not with the method.
4. Link the data analysis to the method evaluation. For example, if you wrote about a qualitative observation that affected your data, then this was likely caused by a variable that wasn’t controlled in your method.

METHOD STRENGTHS

Complete the following:

• Think of the aspects of the method that had a positive impact on the quality or relevance of your data.
• Explain how they positively affected your data.
• Use the list below as a guide to possible method strengths. You DO NOT need to write about ALL of them:
• Measuring method or instrument was very precise.
• The quantities used were large enough.
• There were variables that were controlled very well.
• The range of the independent variable was appropriate to show the relationship between variables.
• The method was very close to how things would happen in the outside world (ie. not a highly controlled environment).
• We can use the results of the method to gain information about a lot of different situations.
• The information gained in the investigation provides a lot of information for solving a larger overall problem.

METHOD LIMITATIONS AND IMPROVEMENTS

Complete the following:

• Choose two or three aspects of your method that reduced the quality or relevance of your data.
• Use the list below as a guide to possible method limitations. You DO NOT need to write about all of them:
• Measuring method or instrument was not very precise.
• The quantities used were too small.
• There were variables that were not controlled very well or were not even considered.
• The range of the independent variable was limited, and you might get different results if you made the independent variable much higher, much lower or much broader.
• The method had a lot of differences to how things are in the world outside the lab environment (ie. the conditions of the experiment were too ‘perfect’).
• The method is very specific to a certain situation, and we can’t use the method to gain information about a lot of different situations.
• The information gained in the investigation provides little information for solving a larger overall problem.
• Suggest ways to improve the method. Imagine you had unlimited time and/or funds.

METHOD LIMITATIONS AND IMPROVEMENTS

FURTHER INVESTIGATION

Complete the following:

• Outline one or two aspects of the overall problem or topic that the method does not address.
• Suggest ways that the method could be altered to provide more information about the problem or topic.

CONCLUSION