QualificationBTEC Level 3 National Diploma in Applied ScienceBTEC Level 3 National Extended Diploma in Applied Science

Unit number and title Unit 6: Investigative Project

Learning aim(s) (For NQF only)

C: Undertake the project collecting, analysing and presenting the results

Assignment title Project implementation

Assessor Ms Roczniak

Issue date 28th November

Hand in deadline Sunday 10 th December, Midnight

Criteria covered by this task:Unit/Criteria reference To achieve the criteria you must show that you are able to:

C.P4 Demonstrate practical skills to assemble relevant apparatus/equipment and materials, and carry out the project using safe working practices.

C.P5 Accurately collect, analyse and present the results obtained.

C.M4 Justify the choice of experimental and data analysis techniques usedas a means of increasing accuracy, reliability and validity.

Checklist of Work

Done? Description of work needed Help/guidance pagesPictures of your set up equipment and at stages of your investigation

n/a

Filled in table of your results 3Mean calculated in table 3Hand drawn graph for your results, scanned in 4-6Justification of choice of graph 5Range bars drawn onto your graph 7Standard Deviation calculated 8-12Justification of standard deviation 12Assessment of accuracy 13Assessment of precision 14Assessment of reliability 14Assessment of validity and method justified 15

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1. Carrying Out your Investigation

All the background research, literature review and planning has now be completed and the practical element of the investigative project is about to begin.

The setting up stage of the scientific equipment is of fundamental importance to the investigation and you must ensure that the health and safety information gathered has been understood and is in place.

Your skills in using the equipment and observation of important experimental events will need to be perfected so that your results are both valid and reliable.

Throughout your carry out your teacher will be observing your use of equipment in order to assess your practical skills. Skills that will be assessed are:

Awareness of health and safety issues Competence in equipment assembly Ability to manipulate equipment to obtain results Observation and record keeping practices Adherence to good laboratory practice Measurements are taken with accuracy and precision

Rough test results

As you carry out your practical investigation, record your results in rough below:

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Hint and Tips for a successful investigative carry out

1. Have a physical copy of your method and equipment list in front of you2. Put on a lab coat and safety glasses before you begin and keep them on

throughout3. Collect all of your equipment from your equipment list and have it in front of you

laid out before you begin4. Check off all of your equipment from your list5. Have your set up checked by your teacher or a technician before you begin6. Carefully follow your method step by step7. Do not rush8. Record your results to appropriate decimal places

Key Terms

Good Lab PracticeSystem of regulation which ensures that tests carried out are well planned, reliable and have well assessed hazards

AccuracyCloseness of readings to the actual value

PrecisionThe closeness of measurements to each other.

1 2 3 Mean

Collecting the data must be completed with a high degree of integrity, this means that you must record the results exactly as you find them and not as you would expect or like to see. Record your data with precision, to correct number of decimal places based on the equipment used.

Justification of use of no decimal places:

When typing up your report, below your results justify why you have not recorded the time to 0 decimal places or your volume of oxygen collected to 1 decimal place.

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Hints and Tips:

If you are recording time, your reactions are not split second responsive; therefore, you should not record time in the decimal places only whole seconds. If you are recording volume of oxygen then the measuring cylinder may be divided in such a way that it allows for recording to 1 decimal place.

The number of decimal places should be consistent through the entire table, including your mean. Round up or down where appropriate.

2. Presenting your Results

Visual displays of data provide valuable information to the reader in a much shorter time scale and contain the essential information.The most common method to display data is using graphs. The type of graph used depends on the kind of data that is to be displayed.

Type of data Description ExamplesDiscrete Data that can only take certain

values.For example: the number of students in a class (you cannot have half a student only 1 or 2 etc).Labels on axes are for measured values and whole numbers.Typically presented in bar charts or pie charts.

Number of masses addedNumber of students who have chosen a particular subjectResults of rolling two dice

Continuous Data that can take any value and can be subdivided into finer increments.E.g. 1m and 2 m can be subdivided into smaller sizes 1.1m, 1.2 m etcLabels on x axis are appropriate number values.Typically presented in a line graph, sometimes if intervals are needed (30-34, 35-39) also a histogram.

TemperatureMassLengthVolumeTimeDistance

Categorical Specific word labels with whole number data (like discrete).Typically presented in bar charts.

Names of:MetalsPlantsCompoundsanimals

What type of data are your results? How should you present it in a graph? You will need to justify your choice for the meritDrawing graphs

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Quick test of your understanding

For each of the below examples give the type of data using the above table and the type of graph it should be presented in.

a) The heights of pupils in class 3Ab) The number of chocolates in 500g boxesc) The time taken for athletes to run 100m

Graphs should be able to stand alone in your report. Including the following aspects will ensure that the focus of your investigation can be viewed immediately from your graph document:

1. Heading – the title of the investigation and the variables plotted2. Labelled axes – this should include the correct units and scales of measurements, if

you have plotted the mean make sure you state that.3. y axis non-zero indicator –y axis should always have a value at the origin (point at

the left hand corner). Sometimes, the scale does not have to start at zero. You can draw a ‘zigzag’ between the origin and the first scale point or you can start your y axis at a value other than zero.

4. Range bars – these show the variation in measurements. (see page 7)

Examples of graphs

Justification of Graph Choice

After you have drawn your graph you need to justify your choice of graph. Why a bar chart/line graph/pie chart etc? Refer to the type of data that you have collected (see page 4). Additionally. Justify your choice of drawing range bars onto your graph (see page 7). This does not need to be long, a few sentences or a small paragraph.

Badly drawn line graphs

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Look at the graphs, identify the mistakes by writing on them and/or circling any errors.None of these graphs have been given titles, do not include that in your list of errors, focus on the drawing.

Drawing Range bars

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Range bars show the variation in the data for each value. The upper bar shows the largest, maximum recorded measurement and the lower bar is the lowest recorded measurement. Both bars emanate from the plotted mean value.

Range bars are a visual representation of the spread of data at each value. It can give an idea of the precision and reliability of the measurements at each value – the larger the range bars, the bigger the spread of data and therefore the less precise the readings are resulting in a lower reliability.

From the graph above measurements at 1 and 5 have the largest range bars and are therefore the least precise and have the lowest reliability, whereas, measurements at 3, 9 and 10 are most precise as they have the smallest range bars and therefore have the highest reliability.

3. Processing and Analysing your data

Researchers often want to look at the spread of the data, that is, how widely the data are spread across the whole possible measurement scale.

There are three measures which are often used for this:

The range is the difference between the largest and smallest values.

The standard deviation measures the average spread around the mean, and therefore gives a sense of the ‘typical’ distance from the mean.

The variance is the square of the differences from the mean. They are calculated by:

1. calculating the difference of each value from the mean; 2. squaring each one (to eliminate any difference between those above and below the

mean);3. summing the squared differences;4. dividing by the number of items minus one.

This gives the variance.

To calculate the standard deviation, take the square root of the variance.

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Standard Deviation

Practice problem 1:

Practice Problem #1: Calculate the standard deviation of the following test data by hand. Use the chart below to record the steps.

Test Scores: 22, 99, 102, 33, 57, 75, 100, 81, 62, 29

Step 1 – count the number of values - 10

Step 2 – calculate the mean = 66

Step 3 – calculate Ʃ(x-ẋ)2, use a table to track this and organise your calculation.

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Step 4 – Divide your Ʃ(x-ẋ)2 by the number of values in eth sample:

8338 ÷ 10 = 833.8

Step 5 – finally square root this number √833.8 = 91.31

Standard Deviation of your results

Value 1_____________ (e.g. pH 4, 0.5M, 0.5cm etc)

Mean_______________

Value (from your repeats)

x

Measurement – mean

x-ẋ

(measurement-mean)2

(x-ẋ)2

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229910233 57 75 10081 62 29

-44 33 36-33-9 9 3415 -4-37

193610891296108981811156225161369

8338

Ʃ (x-ẋ)2

Total from table ÷ 3 [Ʃ (x-ẋ) 2 ] ____________________

N

Square root of the above answer __________________

Value 2_____________

Mean_______________

Value (from your repeats)

x

Measurement – mean

x-ẋ

(measurement-mean)2

(x-ẋ)2

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Ʃ (x-ẋ)2

Total from table ÷ 3 [Ʃ (x-ẋ) 2 ] ____________________

N

Square root of the above answer __________________

Value 3_____________

Mean_______________

Value (from your repeats)

x

Measurement – mean

x-ẋ

(measurement-mean)2

(x-ẋ)2

Ʃ (x-ẋ)2

Total from table ÷ 3 [Ʃ (x-ẋ) 2 ] ____________________

N

Square root of the above answer __________________

Value 4_____________

Mean_______________

Value (from your repeats)

x

Measurement – mean

x-ẋ

(measurement-mean)2

(x-ẋ)2

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Ʃ (x-ẋ)2

Total from table ÷ 3 [Ʃ (x-ẋ) 2 ] ____________________

N

Square root of the above answer __________________

Value 5_____________

Mean_______________

Value (from your repeats)

x

Measurement – mean

x-ẋ

(measurement-mean)2

(x-ẋ)2

Ʃ (x-ẋ)2

Total from table ÷ 3 [Ʃ (x-ẋ) 2 ] ____________________

N

Square root of the above answer __________________

Justification of using standard deviation

After you have calculated your standard deviation you must justify your use of it and explain what it shows you. This part does not need to be long perhaps just a few sentences but it is needed

4. Assessment of accuracy and reliability

Your investigation findings should be assessed in terms of accuracy of results and precision of readings and measurements.

Accuracy

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The accuracy of each measurement depends on the quality of the measuring apparatus and the skill of the scientists taking the measurement. If the apparatus is faulty, or the scientists make a mistake, the measurement may be inaccurate.

Accuracy of your results can be briefly determined if your results are close to their true and expected value. For example, if you investigated pH did your results suggest an optimum that is close to the true pH optimum value of catalase?

State all the ways that you ensured your results were accurate, justifying choice of method and equipment.

State all the ways that there may have been sources of inaccuracies in your experiment and suggest improvements where appropriate.

Notes on accuracy:

Precision and Reliability

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Unlike accuracy, which looks at the closeness of the results to the true value, precision is how close the repeat measurements are to each other.

To comment on precision look at your range bars. Are they large or small? Do they show a large range between repeats or not? The smaller the range the more precise your measurements are.

For data to be reliable, there must be a small variation within the values, even though there is always some variation in every set of measurements. If the data is similar after many repeats you can be confident that the results are reliable.

Notes on precision and reliability:

5. Validation of method and results

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In general, validity is an indication of how sound your research is. More specifically, validity applies to both the design and the methods of your research. Validity in data collection means that your findings truly represent the hypothesis you are claiming to measure and investigate. Valid claims are solid claims. Validity will be informed by your accuracy and your reliability.

The scientific method you have used should have been well designed and well planned. If this is the case, experimental errors or bias can be greatly reduced or eliminated and your overall confidence in the investigation and its results can be high. To establish whether the method you used is fit for purpose, you must ask yourself, ‘Did the method allow me to fully investigate the hypothesis?’ and ‘Could I have made any improvements?’ To establish whether a science investigation is valid, you need to ask yourself ‘Will someone be able to repeat my investigation and get the same results or similar results?’

Validity is affected by flaws within the study itself such as not controlling some of the major variables (a design problem), or problems with the research instrument (a data collection problem).

Notes on validity:

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