Scientific Enquiry

Question 1

Describe a suitable control for an investigation and the purpose of controls

Answer 1

When setting up an investigation all conditions and equipment must be the same - apart from the variable being investigated.

Example
Investigate the effects of temperature on catalase activity.

set up two tubes each with a given volume of substrate
set up one with catalase
set up one with an equal volume of water or boiled catalase
both tubes should be set up at the same temperature
Using these conditions we can show that any differences in results are due to the effects of temperature on the catalase and nothing else.

Controls are used in an experiment to ensure that the results found are because of the variable being investigated.

Question 2

Suggest improvements to experiments

Answer 2

Most experiments can be improved. This can make the results more reliable

Potential issues:
limitations in equipment
further experiments could be needed to validate a conclusion
When looking at an experiment in an exam, you may or may not have seen anything like it before. Ask yourself these questions:

Are there any obvious errors?
How have they collected the results? Are the results accurate?
Look at the equipment, could this be improved?

Question 3

Suggest how to increase reliability of an investigation

Answer 3

There are various ways to increase the reliability of an investigation:

repeat the investigation and calculate an average
increase the number of samples taken
increase the number of subjects used (living animals)

Question 4

Suggest how to increase validity of an investigation

Answer 4

Increasing the validity of an investigation ensures that the results collected relate to the independent variable alone. All other variables and factors should be controlled as accurately as possible.

Investigation validity can be increased by:

checking for any obvious errors
reviewing the way in which results were collected
reviewing the accuracy of results
ensuring equipment is suitable, and improving equipment if necessary
ensuring technique is appropriate, and improving technique if necessary

Question 5

Describe the independent and dependent variable

Answer 5

The independent variable is the variable that was changed during an investigation.

The dependent variable will be the results that have been collected throughout the investigation.