Aim & Variables
State the purpose of an aim in a scientific investigation.
To clearly state what the investigation is testing or determining.
State one feature of a scientifically valid hypothesis.
It must be testable.
Which type of graph should be used when plotting oxygen production against temperature?
A line graph
A catalase experiment showed activity increased from 10°C to 40°C before falling at 50°C. State one possible reason for the decrease at 50°C.
Enzyme denaturation.
State one reason new drugs must be tested before use.
To determine safety, effectiveness, or appropriate dosage.
A student investigates the effect of temperature on catalase activity. Identify the independent variable.
Temperature
A hypothesis states: “Increasing hydrogen peroxide concentration will increase oxygen production by catalase.” Identify the independent variable.
Hydrogen peroxide concentration
Which axis should contain the independent variable?
The x-axis
Define a random error.
An unpredictable error that causes results to vary irregularly around the true value.
Describe the purpose of a placebo group in a clinical trial.
It acts as a control group for comparison with the treatment group.
A student investigates the effect of temperature on catalase activity by measuring oxygen produced per minute. Identify the dependent variable.
Rate of catalase activity, measured as oxygen production per minute.
Explain why the hypothesis “What happens to photosynthesis when light intensity changes?” would not gain full marks in Criterion 3.
It is a question, not a testable statement, and it does not clearly predict the effect of the IV on the DV.
Define an outlier.
A data point that differs substantially from the other results in a dataset.
Define a systematic error.
A consistent error that shifts all measurements in the same direction from the true value.
Define informed consent.
Participants are provided with sufficient information about the trial so they can make a voluntary decision to participate.
Explain the purpose of a control group in an experiment.
A control group acts as a comparison and helps determine whether changes in the dependent variable are caused by the independent variable.
Write a suitable hypothesis for an investigation into the effect of temperature on enzyme activity.
Increasing temperature will increase enzyme activity up to an optimum temperature, after which activity will decrease due to denaturation.
Describe one way to improve the reliability of experimental results.
Increase the number of replicates, repeat the experiment, or calculate averages.
A student only used three replicates in an experiment. Explain why this is a limitation.
A small number of replicates increases the effect of random error and reduces reliability.
Explain the purpose of a double-blind clinical trial.
Neither participants nor researchers know who receives the treatment, reducing bias and placebo effects.
For an investigation into light intensity and photosynthesis, identify one independent variable, one dependent variable and two controlled variables.
IV: Light intensity. DV: Rate of photosynthesis. Controlled variables could include temperature and carbon dioxide concentration.
Explain the difference between a hypothesis and a scientific theory.
A hypothesis is a testable prediction, whereas a theory is a well-supported explanation based on extensive evidence collected over time.
Compare accuracy, reliability and validity.
Accuracy is how close results are to the true value, reliability is the consistency of results, and validity is whether the experiment measures what it intended to measure.
State the three key components that should appear in a scientific conclusion.
The outcome of the investigation, evidence from the results, and whether the hypothesis was supported or rejected.
Outline the major stages involved in testing a new drug before widespread use.
Preclinical testing using models and cells, animal testing, and human clinical trials involving healthy volunteers and patients.