9.9 - Assignment Skills

What the National 5 assignment is

• The assignment is coursework that sits alongside the question paper in National 5 Biology.
• It involves researching a biology topic, carrying out or drawing on an experiment, handling the data, and writing it up as a report.
• It's worth about 20% of the course award, so it tests skills the written paper can't:
  • Collecting your own data
  • Presenting it
  • Referencing where your information came from

The two stages

1. Research and investigate - Settle on an aim, find out the biology behind it, and gather data. This means both your own experimental results and figures from other sources such as textbooks or websites.
2. Write it up under exam conditions - Turn your research into a structured report containing a table, a graph, an analysis, a conclusion, and an evaluation.

Skills you already have

• Nearly every skill the report needs is one already met in this topic:
  • Choosing variables and a fair test
  • Building a table
  • Doing the calculations
  • Drawing a graph
  • Reading it
  • Drawing a conclusion
  • Evaluating the method
  • Planning the whole thing
• What's new is putting these skills together into one piece of work and crediting your sources.

Choosing an aim and the underlying biology

• The assignment starts with an aim: a clear statement of what you are trying to find out.
• A good aim names the two variables and reads as "how does X affect Y".
  • Example: "to find out how temperature affects the rate at which the enzyme catalase breaks down hydrogen peroxide".
• This wording hands you the two variables straight away, and it is something you can actually test:
  1. Independent variable - The one you change (temperature)
  2. Dependent variable - The one you measure (the rate of the reaction)

The underlying biology

• Behind the aim sits the biology that explains why you expect a result.
• For the catalase aim, the background is how enzymes work:
  • They speed up reactions
  • They have an optimum temperature
  • They denature and stop working when they get too hot
• Setting this out shows you understand the topic, and gives you something to compare your results against at the conclusion.

Keep the aim narrow enough to investigate in the time you have

• "How does temperature affect catalase" is testable in a lesson.
• "What affects enzymes" is too broad to plan or measure.

Collecting and handling data

The core of the assignment is data you collect yourself, and the rules that make any investigation sound apply here too. Three things matter most.

Make it a fair test

• Change only the independent variable, and keep every other variable the same.
• If you're testing temperature, then the volume and concentration of your solutions, the amount of enzyme, and the timing all stay constant.
• Only then can a change in your result be put down to the temperature and nothing else - which makes the result valid.

Repeat for reliability

• Take each reading more than once and find the mean.
• A single reading might be an anomaly, and consistent values in the repeats show the results are reliable.
• Repeating is what lets you call your results reliable.

Gather comparison data

• Find data from a source other than your own experiment - a textbook, a website, or a database - that's relevant to your aim.
• This lets you compare your results against it in the report.
• Note where it came from as you collect it, because the source has to be referenced.

Using a control

• A control is a version with the factor you're testing left out, so you can be sure the effect you see is caused by the variable you changed.
• In an enzyme investigation, a tube with the enzyme boiled first (so it no longer works) shows that any reaction in the other tubes was down to the working enzyme.

Record your own readings straight into a table as you go, so nothing is lost.

Presenting your data

The report presents your data in a table and a graph, drawn to the same rules as the question paper.

The table

• The independent variable goes in the first column, with its values in order.
• Add a column for each repeat of the thing you measured, then a final column for the mean.
• Write every heading as "quantity / unit" - unit in the heading, plain numbers below. This is the convention markers look for.
• Record every reading in a column to the same precision.

The graph

The graph turns the mean results into a picture. The type you draw depends on the independent variable - a bar chart for a discrete variable and a line graph for a continuous variable:

• Line graph - Use when the independent variable is continuous - a number that can take any value in between (e.g. temperature, time, concentration). Plot the points accurately and join them with a ruled line from point to point.
• Bar chart - Use when the independent variable is discrete or categoric - separate groups with no in-between values (e.g. different species, food types, habitats).

Whichever you draw:

• Label both axes with the quantity and its unit.
• Choose a linear scale that fills the grid.
• Give the graph a title.

Analysing data and drawing a conclusion

• Analysing the data means describing what the table and graph show, pulling out the trend, and doing any calculation that makes the pattern clearer - such as a percentage change or a rate.
• Read the graph well by giving:
  • The direction of the trend
  • Figures from the axes to back it up
  • Where the line levels off or peaks

Writing the conclusion

• The conclusion answers the aim. You set out to find how X affects Y, so the conclusion states how X affected Y, using your own results.
• A good conclusion names both variables, gives the direction, and ties back to the biology from your background.
• Example for the catalase aim: "as the temperature increased from 10 to 40 °C the rate of reaction increased, reaching a maximum at 40 °C, then fell at higher temperatures as the enzyme denatured".

Comparing with your source data

• You must also compare your results with the data gathered from your source, giving both similarities and differences.
• Similarities - Where the two agree, e.g. both show the rate rising with temperature up to an optimum.
• Differences - Where they don't, e.g. your optimum at 35 °C when the source gives 40 °C.
• A comparison that says only "my results matched" or only "my results were different" has done half the job.

Evaluating the investigation

• The evaluation judges how well your investigation worked. It has two halves - both are needed.
• Half 1 - Name a real factor that affected the validity, reliability, or accuracy of your investigation.
• Half 2 - Say one of three things about that factor.
• The factor should be a genuine feature of what you did - not a generic "human error".

Half 1 - Name the factor affecting validity, reliability, or accuracy

Each word points at a different kind of weakness:

• Validity - The fair test. A variable you didn't keep the same affects validity - e.g. a water bath that cooled during the run, so temperature wasn't the only thing changing.
• Reliability - The repeats. Readings that scattered widely, an anomaly you had to leave out, or too few repeats to be sure of the mean.
• Accuracy - How close each reading is to the true value. An end-point judged by eye, a volume added drop by drop, or a stopwatch started late.

Half 2 - Say one of three things about it

Any one of these completes the evaluation:

1. What could have been done - e.g. a thermostatically controlled water bath for a temperature that drifted, a colorimeter for an end-point judged by eye, or more repeats for scatter.
2. What you actually did - e.g. you discarded the anomaly before finding the mean, or you re-ran the reading.
3. The evidence you saw - e.g. two of your three repeats at 30 °C differed by 40 seconds.

Writing up and referencing

• The final report follows a clear structure, so a reader can follow it from aim to conclusion.
• Working through the sections in order means nothing gets left out.

A typical report order

1. Title and aim
2. The underlying biology
3. The method
4. The results, as a table and a graph
5. An analysis
6. A conclusion that answers the aim
7. An evaluation
8. A list of references

Referencing

• Referencing is the part unique to the assignment: whenever you use information or data from somewhere other than your own experiment - a textbook, a website, a database - you credit where it came from.
• The test of a reference is whether someone else could retrieve the exact source from it:
  • Website - The full address of the page the data came from, not the site's home page.
  • Book - Its title, author, and the page.
• Referencing shows that your background biology and comparison data rest on real sources. It's a requirement of the write-up, not an optional extra.

Two habits that strengthen the report

1. Use the correct biological terms throughout - the same ones you'd use in the question paper.
2. Keep the report in your own words - copying a source word for word, without crediting it, is not acceptable.

Common exam questions

Question 1

Roughly how much of the National 5 course award is the assignment worth?

About 20% - a fifth of the grade - so it carries the marks for skills the written paper cannot test, such as collecting your own data and referencing sources.

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Question 2

What makes a good aim for the assignment?

One that names both variables and is narrow enough to test, reading as "how does X affect Y", such as "how does temperature affect the rate at which catalase breaks down hydrogen peroxide".

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Question 3

Why should you repeat your readings and take a mean in the assignment?

Because a single reading might be an anomaly, and getting consistent values in the repeats is what makes the result reliable.

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Question 4

You collected results for the rate of a reaction at five different temperatures. Should you draw a line graph or a bar chart?

A line graph, because temperature is a continuous variable with values in between; a bar chart is for separate categories such as different species.

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Question 5

A conclusion in the report should do what?

Answer the aim, by stating how the independent variable affected the variable you measured, using your own results and linking back to the biology in your background.

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Question 6

What does the comparison between your results and the source data have to include?

Both similarities and differences: where the two agree, such as the same overall trend, and where they do not, such as a different optimum temperature. Saying only that they matched, or only that they differed, is half a comparison.

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Question 7

A student's evaluation says "the water bath cooled during the run". What is missing?

Two things: which of validity, reliability, or accuracy it affected (validity, because temperature was no longer the only variable changing), and either what could have been done about it, what was done, or the evidence for it - such as using a thermostatically controlled water bath.

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Question 8

Why must you reference the sources you used in the assignment?

Because any information or data that is not your own must be credited so a reader can retrieve the source and check it; for a website that means the full address of the page, not the home page. Referencing is a required part of the write-up.