science skills- experiments

Independent variable:

the variable that is being manipulated/changed. A fair test will, usually, only have one IV.

Dependent variable:

the variable that is being measured.

Controlled variable

A variable that is kept the same across all trials.

Control group

A treatment that is not exposed to the independent variable.

types of scientific investigations

Controlled Experiments

Correlational Study

Fieldwork

Literature Review

Models and Theories

controlled experiment

An investigation of the relationship between an independent variable and a dependent variable, controlling all other variables. Only one variable should change.

Correlational Study

Planned observation and recording of events and behaviours that have not been manipulated or controlled to understand the relationships/associations that exist between variables.

fieldwork

Observing and interacting with an environment, in an attempt to determine correlation, rather than a causal relationship. It may involve qualitative and/or quantitative observations and sampling, observation, interviews and questionnaires.

litreture review

Analysis of secondary data related to other people's findings in order to answer a question or provide background information to help explain observed events, or as preparation for an investigation to generate primary data.

modeling

Involves the construction of a physical, conceptual or mathematical model, such as a small- or large-scale representation of an object, concepts or equation.

stimulation

A process of using a model to study the behaviour of a real or theoretical system.

experimental group meaning

the experimental group is the group that receives the specific treatment or intervention being tested in an experiment

poster title

Should be written as a question that includes the independent and dependent variables.

Graph title

Should be written as a statement that includes the independent and dependent variables.

aim

To investigate the effect of the independent variable on the dependent variable.

.To investigate, to determine etc.

introduction what to include

An introduction to the topic (what are enzymes, what is photosynthesis etc.).

Some context and background (about what catalase/trypsin is, their optimal pH & temperature).

To tell your reader about the research you plan to carry out.

To explain why your research is important.

REFER to the Research Questions at the bottom of the "Assessment Summary sheet" as a guide

hypothesis

If the independent variable is increased/decreased the dependent variable will increase/decrease (units).You do not need a "because".

elements of method

Must include:

The independent, dependent and controlled variables,control groups, and repeatability specifically listed.

results element

A table including- All raw data included in a table with title.- Relevant observations included.

graph results element

A graph including

One mark for each of the following:

Axes labelled (with units)

Accurate plotting of data

Appropriate scale with even intervals

Appropriate title with IV and DV included

outliers

Data points that do not fit a pattern or trend, for example they lie a long way from other results.

Continuous data:

data that exists on a continuum/a scale with no defined groups is represented as a line graph.e.g. temperature (oC), pH (colour change), height (cm)

Categorical data:

data that has defined groups/categories, is represented as a bar graph.e.g. temperature (cold, medium, hot), ph (low, neutral, high), height (short, medium, tall)

what to include in discussion

Describe trends or patterns in your results (use your data that you collected)

if you don't reference your data you won't get any marks.

Explain your results using scientific reasoning

talk about the what you observed - what was occuring? How can your results be explained?

Recognise some errors that may have occurred and explain why they were unavoidable.

Remember the difference between a MISTAKE and an ERROR. Also know different types of errors (personal, random and systematic)

Discuss any limitations in your experimental design.

Explain your experiment in terms of its accuracy, precision, reproducibility, repeatability and validity of measurements

How would you improve your experiment based on these results/errors?

one sentence summary

A one sentence summary reporting the major finding of the investigation was provided.

Your one sentence needed to reflect results - trypsin/enzyme activity.

Should be specific eg. a pH of 7 had the greatest trypsin activity.

e.g. An oxygen concentration of 30% in animal cells resulted in the highest rate of cellular respiration.

conclusion

1.Restate purpose of experiment

2.Summarise data

3.State whether your results support or contradict your hypothesis.

errors

Errors are the difference between the measured value and the true value of what is being measured.

An error is not a mistake, unless it is a personal error.

There are three main categories of error: systematic, random and personal/mistakes

random error

Unpredictable variations in all measurements, except for counting.

how to reduce random error impact

Repeat and calculate a mean/average.Increase sample size:As sample size increases, the influence of any single data point/outlier becomes smaller.

systematic error

Variations in the measurement that differ from the true value by a consistent amount every time.

how to reduce impacts of systematic errors

Making sure that measuring instruments are operating correctly.

Cannot be improved by repeated measurements.

personal errors

Mistakes or miscalculations.

how to reduce personal error effects

Eliminated by performing the experiment again correctly the next time.

Reproducibility:

Somebody else (a different observer) conducts your experimental design (but using different equipment, different place etc.), and gets the same/very similar results, it is said to be reproducible.

Repeatability:

You, yourself, repeat your experiment, under the same conditions (including the same equipment, materials etc.) and gather the same/very similar results.

accuracy

refers to the closeness of an experimental measurement to an accepted or known, or 'true' value.

precision

refers to the closeness of repeated measurements to each other.Values will always differ from one another because of random errors.

validity

It measures what it is supposed to be measuring. and an experiment is said to be valid if it is a controlled experiment (only changing one variable).

Limitations

A limitation is a weakness in an experiment's method.

It is not an error as it has not occurred during the undertaking of the experiment but rather an issue with the experimental design itself.

what to include in experimental design

IV

DV

CV

CG

repeat/size sample

ethical concepts

Integrity: commitment to knowledge, understanding and honest reporting whether results are favourable or not.

Justice: commitment to consideration of competing claims, the fair access to the benefits of an action and no unfair burden to a particular group.

Beneficence: commitment to maximisation of benefits and minimisation of harm.

Non-maleficence: commitment to not causing harm that is disproportionate to the benefit.

Respect: commitment to consideration of beliefs, customs, cultural heritage and autonomy

explain this question and answer- Consider the cells that were not given 5 micromoles of rosiglitazone. From which metabolic pathways would cells be obtaining most of their energy and where are these metabolic pathways found in the cell?

Cells would be obtaining most of their energy through aerobic respiration, including the Krebs cycle (in the mitochondrial matrix) and the electron transport chain (on the inner mitochondrial membrane or cristae). Glycolysis also occurs in the cytoplasm but produces less ATP.

question in test- Outline a controlled experiment you would carry out to determine- worth five marks

- add IV

DV

CG

CV

repeatability

expected results if stated

contradictory data

Conflicting results about an expected phenomenon.The results are not what you would expect based on your theoretical understanding.

opinion

the personal belief or viewpoint of an individual which typically has not been verified as fact

anecdote

evidence involving a personal account or report of a previous experience that may provide a certain level of support for a position

ratios

A comparison of two things. 4 dogs : 2 cats, which is showing us that for every 4 dogs this person has, they have 2 cats or simplified as 2 dogs : 1 cat.

percentages

the proportion of a whole, made up by a certain group. 2/6 of the pets are cats. Therefore, 2/6 x 100 = 33% of the pets are cats.

uncertanty in data

All measurements are subject to uncertainty and may have many potential sources of variation, including human capacity in measurement, the nature of the instrumentation used and external factors.

This uncertainty extends to the conclusions that depend on uncertain measurement.

Improving experimental design (fixing limitations) -subjective matter

why is this limiting

improvement

E.g. Time taken for solution to clear/turn a specific colour

Why is this limiting?

Open to observer interpretation

Improvement:

Ensure same observer for each measurement

Use an objective measure, such as a colourimeter or probe

Improving experimental design (fixing limitations)-Limited data points/intervals of measurement

why is this limiting

improvement

Why is this limiting?

If intervals are too big, you might not see all changes to reaction rate (ie. points of denaturation, optimal temperature etc.)

Improvement:

Include more, regular intervals

Improving experimental design (fixing limitations)-No control group

why is this limiting

improvement

Why is this limiting?

Nothing to compare the effect of the independent variable to

Improvement:

Include a control group that is not exposed to the independent variable

Improving experimental design (fixing limitations)

Not controlling all possible variables

why is this limiting

improvement

Why is this limiting?

Something other than the IV may have influenced the results

Improvement:

Ensure the experimental method accounts for all possible variables (pH, temperature, solution concentration, etc.)

Improving the accuracy of an experiment

Large sample size: As sample size increases, the influence of any single data point/outlier becomes smaller.

Repeating and calculating a mean/average:

Equipment with a higher resolution: determining the number of decimal places to which a quantity may be quoted.

Uncertainty in data

All measurements are subject to uncertainty and may have many potential sources of variation, including human capacity in measurement, the nature of the instrumentation used and external factors.

This uncertainty extends to the conclusions that depend on uncertain measurement.

Contradictory data:

Conflicting results about an expected phenomenon.The results are not what you would expect based on your theoretical understanding.

Provisional data

Data that is collected and reported before it has been fully validated, confirmed, or finalized.- Where timely reporting is critical despite potential inaccuracies.

Incomplete data:

Lacks some observations that were intended to be collected. - Poses challenges for analysis and can lead to uncertain conclusions if not properly handled.